IEC 60938-1:1999
(Main)Fixed inductors for electromagnetic interference suppression - Part 1: Generic specification
Fixed inductors for electromagnetic interference suppression - Part 1: Generic specification
IEC 60938-1:1999, applies to inductors designed for electromagnetic interference suppression intended for use within, or associated with, electronic or electrical equipment and machines. It is restricted to inductors for which safety tests are appropriate. This second edition cancels and replaces the first edition published in 1988 and constitutes a minor revision related to tables, figures and references. It also includes Amendment 1 (2006).
Inductances fixes d'antiparasitage - Partie 1: Spécification générique
La CEI 60938-1:1999, s'applique à des inductances conçues pour s'opposer aux perturbations électromagnétiques et destinées à être utilisées dans ou en association avec du matériel et des machines électroniques ou électriques. Elle se limite à des inductances pour lesquelles des essais de sécurité sont souhaitables. Cette deuxième édition annule et remplace la première édition parue en 1988, et constitue une révision mineure, ayant trait aux tableaux, figures et références. Elle inclut également l'Amendement 1 (2006).
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Standards Content (Sample)
INTERNATIONAL IEC
STANDARD
60938-1
QC 280000
Second edition
1999-10
Fixed inductors for electromagnetic
interference suppression –
Part 1:
Generic specification
Inductances fixes d'antiparasitage –
Partie 1:
Spécification générique
Reference number
Numbering
As from 1 January 1997 all IEC publications are issued with a designation in the
60000 series.
Consolidated publications
Consolidated versions of some IEC publications including amendments are
available. For example, edition numbers 1.0, 1.1 and 1.2 refer, respectively, to the
base publication, the base publication incorporating amendment 1 and the base
publication incorporating amendments 1 and 2.
Validity of this publication
The technical content of IEC publications is kept under constant review by the IEC,
thus ensuring that the content reflects current technology.
Information relating to the date of the reconfirmation of the publication is available
in the IEC catalogue.
Information on the subjects under consideration and work in progress undertaken
by the technical committee which has prepared this publication, as well as the list
of publications issued, is to be found at the following IEC sources:
• IEC web site*
•
Catalogue of IEC publications
Published yearly with regular updates
(On-line catalogue)*
• IEC Bulletin
Available both at the IEC web site* and as a printed periodical
Terminology, graphical and letter symbols
For general terminology, readers are referred to IEC 60050: International
Electrotechnical Vocabulary (IEV).
For graphical symbols, and letter symbols and signs approved by the IEC for
general use, readers are referred to publications IEC 60027: Letter symbols to be
used in electrical technology, IEC 60417: Graphical symbols for use on equipment.
Index, survey and compilation of the single sheets and IEC 60617: Graphical symbols
for diagrams.
* See web site address on title page.
INTERNATIONAL IEC
STANDARD
60938-1
QC 280000
Second edition
1999-10
Fixed inductors for electromagnetic
interference suppression –
Part 1:
Generic specification
Inductances fixes d'antiparasitage –
Partie 1:
Spécification générique
IEC 1999 Copyright - all rights reserved
No part of this publication may be reproduced or utilized in any form or by any means, electronic or
mechanical, including photocopying and microfilm, without permission in writing from the publisher.
International Electrotechnical Commission 3, rue de Varembé Geneva, Switzerland
Telefax: +41 22 919 0300 e-mail: inmail@iec.ch IEC web site http://www.iec.ch
Commission Electrotechnique Internationale
PRICE CODE
P
International Electrotechnical Commission
For price, see current catalogue
– 2 – 60938-1 © IEC:1999(E)
CONTENTS
Page
FOREWORD . 4
Clause
1 General. 6
1.1 Scope . 6
1.2 Normative references. 6
2 Technical data. 8
2.1 Units and symbols. 8
2.2 Definitions. 8
2.3 Preferred values. 10
2.4 Marking. 11
3 Quality assessment procedures. 11
3.1 General. 11
3.2 Primary stage of manufacture. 11
3.3 Structurally similar inductors . 11
3.4 Qualification approval procedures . 11
3.5 Quality conformance inspection. 12
3.6 Alternative test methods. 12
3.7 Unchecked parameters . 13
4 Test and measurement procedure . 13
4.1 General. 13
4.2 Standard atmospheric conditions. 13
4.3 Drying . 14
4.4 Visual examination and check of dimensions . 14
4.5 Insulation resistance . 15
4.6 Voltage proof . 18
4.7 Inductance . 21
4.8 Insertion loss . 21
4.9 Robustness of terminations . 21
4.10 Resistance to soldering heat . 22
4.11 Solderability (applicable only for terminations intended to be soldered) . 23
4.12 Rapid change of temperature . 23
4.13 Vibration . 24
4.14 Bump . 24
4.15 Shock . 24
4.16 Container sealing . 24
4.17 Climatic sequence. 25
4.18 Damp heat, steady state. 26
4.19 Temperature rise. 26
4.20 Endurance . 27
4.21 Passive flammability. 27
4.22 Active flammability . 28
4.23 Solvent resistance of marking . 28
4.24 Component solvent resistance. 28
60938-1 © IEC:1999(E) – 3 –
Page
Annex A (normative) Interpretation of sampling plans and procedures as described
in IEC 60410 for use within the IEC quality assessment system for electronic
components (IECQ) . 29
Annex B (normative) Rules for the preparation of detail specifications for capacitors
and resistors for electronic equipment . 30
Annex C (normative) Requirements for earth inductors . 31
– 4 – 60938-1 © IEC:1999(E)
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
FIXED INDUCTORS FOR ELECTROMAGNETIC
INTERFERENCE SUPPRESSION –
Part 1: Generic specification
FOREWORD
1) The IEC (International Electrotechnical Commission) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of the IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, the IEC publishes International Standards. Their preparation is
entrusted to technical committees; any IEC National Committee interested in the subject dealt with may
participate in this preparatory work. International, governmental and non-governmental organizations liaising with
the IEC also participate in this preparation. The IEC collaborates closely with the International Organization for
Standardization (ISO) in accordance with conditions determined by agreement between the two organizations.
2) The formal decisions or agreements of the IEC on technical matters express, as nearly as possible, an
international consensus of opinion on the relevant subjects since each technical committee has representation
from all interested National Committees.
3) The documents produced have the form of recommendations for international use and are published in the form
of standards, technical specifications, technical reports or guides and they are accepted by the National
Committees in that sense.
4) In order to promote international unification, IEC National Committees undertake to apply IEC International
Standards transparently to the maximum extent possible in their national and regional standards. Any
divergence between the IEC Standard and the corresponding national or regional standard shall be clearly
indicated in the latter.
5) The IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with one of its standards.
6) Attention is drawn to the possibility that some of the elements of this International Standard may be the subject
of patent rights. The IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 60938-1 has been prepared by IEC technical committee 40:
Capacitors and resistors for electronic equipment.
This second edition cancels and replaces the first edition published in 1988 and constitutes a
technical revision.
The text of this standard is based on the following documents:
FDIS Report on voting
40/1110/FDIS 40/1136/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 3.
The QC number that appears on the front cover of this publication is the specification number
in the IEC Quality Assessment System for Electronic Components (IECQ).
Annexes A, B and C form an integral part of this standard.
60938-1 © IEC:1999(E) – 5 –
The committee has decided that this publication remains valid until 2005.
At this date, in accordance with the committee’s decision, the publication will be
• reconfirmed;
• withdrawn;
• replaced by a revised edition, or
• amended.
A bilingual version of this publication may be issued at a later date.
– 6 – 60938-1 © IEC:1999(E)
FIXED INDUCTORS FOR ELECTROMAGNETIC
INTERFERENCE SUPPRESSION –
Part 1: Generic specification
1 General
1.1 Scope
This International Standard applies to inductors designed for electromagnetic interference
suppression intended for use within, or associated with, electronic or electrical equipment and
machines. It is restricted to inductors for which safety tests are appropriate.
The combination of two or more inductors within one enclosure is also included.
Inductors within the scope of this standard may also be used to protect apparatus and
machines from electrical noise and voltage or current transients coming from either the supply
or from other parts of the apparatus.
This standard does not necessarily apply in its entirety to inductors intended for use on motor
vehicles, in aircraft or for marine applications.
1.2 Normative references
The following normative documents contain provisions which, through reference in this text,
constitute provisions of this International Standard. For dated references, subsequent amendments
to, or revisions of, any of these publications do not apply. However, parties to agreements
based on this International Standard are encouraged to investigate the possibility of applying
the most recent editions of the normative documents indicated below. For undated references,
the latest edition of the normative document referred to applies. Members of IEC and ISO
maintain registers of currently valid International Standards.
IEC 60027 (all parts), Letter symbols to be used in electrical technology
IEC 60050 (all parts), International Electrotechnical Vocabulary (IEV)
IEC 60062:1992, Marking codes for resistors and capacitors
IEC 60068-1:1988, Environmental testing – Part 1: General and guidance
Amendment 1 (1992)
IEC 60068-2-1:1990, Environmental testing – Part 2: Tests – Tests A: Cold
Amendment 1 (1993)
Amendment 2 (1994)
IEC 60068-2-2:1974, Environmental testing – Part 2: Tests – Tests B: Dry Heat
Amendment 1 (1993)
Amendment 2 (1994)
IEC 60068-2-3:1969, Environmental testing – Part 2: Tests – Test Ca: Damp heat, steady state
Amendment 1 (1984)
IEC 60068-2-6:1995, Environmental testing – Part 2: Tests – Test Fc: Vibration (sinusoidal)
60938-1 © IEC:1999(E) – 7 –
IEC 60068-2-13:1983, Environmental testing – Part 2: Tests – Test M: Low air pressure
IEC 60068-2-14:1984, Environmental testing – Part 2: Tests – Test N: Change of temperature
Amendment 1 (1986)
IEC 60068-2-17:1994, Environmental testing – Part 2: Tests – Test Q: Sealing
IEC 60068-2-20:1979, Environmental testing – Part 2: Tests – Test T: Soldering
Amendment 2 (1987)
IEC 60068-2-21:1983, Environmental testing – Part 2: Tests – Test U: Robustness of
terminations and integral mounting devices
Amendment 2 (1991)
Amendment 3 (1992)
IEC 60068-2-27:1987, Environmental testing – Part 2: Tests – Test Ea and guidance: Shock
IEC 60068-2-29:1987, Environmental testing – Part 2: Tests – Test Eb and guidance: Bump
IEC 60068-2-30:1980, Environmental testing – Part 2: Tests – Test Db and guidance: Damp
heat, cyclic (12 + 12 hour cycle)
Amendment 1 (1985)
IEC 60068-2-45:1980, Environmental testing – Part 2: Tests – Test XA and guidance:
Immersion in cleaning solvents
Amendment 1 (1993)
IEC 60294:1969, Measurement of the dimensions of a cylindrical component having two axial
terminations
IEC 60335-1:1991, Safety of household and similar electrical appliances – Part 1: General
requirements
IEC 60410:1973, Sampling plans and procedures for inspection by attributes
IEC 60617 (all parts), Graphical symbols for diagrams
IEC 60695-2-2:1991, Fire hazard testing – Section 2: Needle-flame test
Amendment 1 (1994)
CISPR 17:1981, Methods of measurement of the suppression characteristics of passive radio
interference filters and suppression components
IEC QC 001002-3:1998, Rules of Procedure of the IEC Quality Assessment System for Electronic
Components (IECQ) – Part 3: Approval procedures
ISO 1000:1992, SI units and recommendations for the use of their multiples and of certain
other units
– 8 – 60938-1 © IEC:1999(E)
2 Technical data
2.1 Units and symbols
Units, graphical symbols, letter symbols and terminology shall, whenever possible, be taken
from the following publications:
IEC 60027
IEC 60050
IEC 60617
ISO 1000
When further items are required they shall be derived in accordance with the principles of the
documents listed above.
2.2 Definitions
For the purpose of this International Standard, the following definitions apply.
2.2.1
type
a group of components having similar design features and the similarity of whose
manufacturing techniques enables them to be grouped together either for qualification approval
or for quality conformance inspection
They are generally covered by a single detail specification.
NOTE – Components described in several detail specifications, may, in some cases, be considered as belonging to
the same type.
2.2.2
style
a sub-division of a type, generally based on dimensional factors.
A style may include several variants, generally of a mechanical order
2.2.3
family (of electronic components)
a group of electronic components which predominantly displays a particular physical attribute
and/or fulfils a defined function
2.2.4
sub-family (of electronic components)
a group of components within a family manufactured by similar technological methods
2.2.5
rated voltage (U )
R
rated voltage is either the maximum r.m.s. operating voltage of rated frequency or the
maximum d.c. operating voltage which may be applied continuously to the terminations of the
inductor at any temperature between the lower category temperature and the rated temperature
NOTE – For inductors with only one winding, the rated voltage should only be applied between one terminal and any
conducting surface with which the case is liable to come into contact in normal use. For inductors having more than
one winding, the rated voltage may be applied across two individual windings.
60938-1 © IEC:1999(E) – 9 –
2.2.6
category voltage (U )
C
maximum voltage which may be applied continuously to an inductor at its upper category
temperature
2.2.7
lower category temperature
minimum external surface temperature for which the inductor has been designed to operate
continuously
2.2.8
upper category temperature
maximum external surface temperature for which the inductor has been designed to operate
continuously
NOTE – The external surface temperature can be affected by internal heating due to the lead-through current. The
terminations are considered to be part of the external surface.
2.2.9
rated temperature
maximum ambient temperature at which an inductor can carry its rated current
2.2.10
rated current
maximum r.m.s. operating current at rated frequency or maximum d.c. operating current which
allows continuous operation of the inductor at the rated temperature. It is assigned by the
manufacturer for one or both of the following conditions:
a) free air (I );
RO
b) with a specified heat sink (I ).
RH
2.2.11
rated inductance (L )
R
inductance value for which the inductor has been designed and which is usually indicated upon it
2.2.12
insertion loss
ratio of the voltage before and after the insertion of the suppressor in the circuit as measured
at the terminations
NOTE 1 – The insertion loss can be measured either with a symmetrical or an asymmetrical test circuit.
NOTE 2 – When expressed in decibels the insertion loss is 20 times the logarithm of the ratio stated.
2.2.13
asymmetrical test circuit
a test circuit in which the inductor under test is connected with a coaxial cable of which the
outer conductor constitutes a return path for high-frequency current
[CISPR 17:1981, 3.5 modified]
2.2.14
symmetrical test circuit
a test circuit in which the inductor under test is connected with screened conductor pairs in
which the asymmetrical voltage is small enough to be neglected
[CISPR 17:1981, 3.6 modified]
– 10 – 60938-1 © IEC:1999(E)
2.2.15
insulated inductor
an inductor in which all terminations connected to a section may be raised to a potential
different (but not less than the rated voltage) from that of any conducting surface with which
the case is liable to come into contact in normal use
2.2.16
uninsulated inductor
an inductor in which at least one of the terminations connected to a section cannot be raised to
a potential different (but not less than the rated voltage) from that of any conducting surface
with which the case is liable to come into contact in normal use
2.2.17
electromagnetic interference suppression inductor
an inductor which at mains frequency has a low impedance, but which at radio frequency has a
high inductive impedance
NOTE 1 – It may be used for reducing the interference at frequencies caused by electrical equipment.
NOTE 2 – These inductors are sometimes known as RF chokes.
2.2.18
current-compensated inductor
an inductor having more than one winding on a single core arranged in such a way that the
resultant magnetization caused by the current is near zero
2.2.19
earth inductor
an inductor connected in the earth lead of an equipment.
For requirements for earth inductors, see annex C
2.2.20
thyristor inductor
an inductor used in thyristor controlled circuits
2.2.21
mains inductor
an inductor intended for direct electrical connection to the supply mains
NOTE – This inductor may form part of an equipment.
2.2.22
TV choke
an inductor designed to reduce interference mainly in the frequency range 30 MHz to 300 MHz
NOTE – Unencapsulated, non-current compensated TV chokes are not within the scope of this specification, but
should be considered as part of the equipment wiring.
2.2.23
visible damage
visible damage which reduces the usability of the inductor unit for intended purpose
2.3 Preferred values
Each sectional specification shall prescribe the preferred values appropriate to the sub-family
covered by that sectional specification.
60938-1 © IEC:1999(E) – 11 –
2.4 Marking
2.4.1 General
The sectional specification shall indicate the identification criteria and other information to be
shown on the inductors and the packing.
The order of priority for marking small inductors shall be specified.
2.4.2 Coding
When coding is used for tolerance or date of manufacture, the method shall be selected from
those given in IEC 60062.
3 Quality assessment procedures
3.1 General
When these standards are used for the purpose of a full quality assessment system such
as the IEC Quality Assessment System for Electronic Components (IECQ), compliance to 3.4
or 3.5 is required.
When these standards are used outside quality assessment systems for purposes such as
design proving or type testing, the procedures and requirements of 3.4.1 and 3.4.3 may be
used, but the tests and parts of tests shall be applied in the order given in the test schedules.
Before inductors can be qualified according to the procedures of this clause the manufacturer shall
obtain the approval of his organization in accordance with the provisions of IEC QC 001002-3.
For certification by an independent test laboratory the procedure of 3.4.3 shall be sufficient,
except that the test laboratory will produce the evidence of conformance.
3.2 Primary stage of manufacture
The primary stage of manufacture is the winding of the inductive element(s).
3.3 Structurally similar inductors
The grouping of structurally similar inductors for the purpose of qualification approval and
quality conformance inspection shall be prescribed in the sectional specification.
3.4 Qualification approval procedures
3.4.1 Eligibility for qualification approval
The manufacturer shall comply with 3.1.1 of IEC QC 001002-3.
3.4.2 Application for qualification approval
The manufacturer shall comply with 3.1.3 of IEC QC 001002-3.
3.4.3 Test procedure for qualification approval
In addition to the requirements of 3.4.1 and 3.4.2, the manufacturer shall produce test evidence
to show conformance to the specification requirements on the fixed sample size test schedule
given in the sectional specification.
– 12 – 60938-1 © IEC:1999(E)
The specimens taken to form the sample shall be selected at random from current production
or as agreed with the National Supervising Inspectorate (NSI).
3.4.4 Granting of qualification approval
Qualification approval shall be granted when the procedures in accordance with 3.1.4 of
IEC QC 001002-3 have been completed satisfactorily.
3.4.5 Maintenance of qualification approval
Qualification approval obtained as part of a quality assessment system shall be maintained by
regular demonstration of compliance with the requirements for quality conformance (see 3.5).
3.5 Quality conformance inspection
The blank detail specification(s) associated with the sectional specification shall prescribe the
test schedule for quality conformance inspection. This schedule shall also specify the grouping,
sampling and periodicity for the lot-by-lot and periodic inspection.
Operation of the switching rule for reduced inspection in group C is permitted in all sub-groups
except endurance. Sampling plans and inspection levels shall be selected from those given
in IEC 60410.
If required, more than one schedule may be specified.
3.5.1 Certified test records of released lots
When certified test records are requested by a purchaser, they shall be specified in the detail
specification.
3.5.2 Delayed delivery
Inductors held for a period exceeding three years (unless otherwise specified in the detail
specification) following the release of the lot shall, before delivery, be re-examined as specified
in the sectional specification.
Once a lot has been satisfactorily re-inspected, its quality is re-assured for three years from the
date of re-inspection.
3.5.3 Release for delivery before the completion of group B tests
When the conditions of IEC 60410 for changing to reduced inspection have been satisfied for
all group B tests, the manufacturer is permitted to release components before the completion
of such tests.
3.6 Alternative test methods
See 3.2.3.7 of IEC QC 001002-3 with the following details:
In case of dispute, for referee and reference purposes only the specified methods shall be
used.
60938-1 © IEC:1999(E) – 13 –
3.7 Unchecked parameters
Only those parameters of a component which have been specified in a detail specification and
which are subject to testing can be assumed to be within the specified limits.
It cannot be assumed that any unspecified parameter will remain unchanged from one
component to another. Should it be necessary, for any reason, for further parameters to be
controlled, then a new, more extensive specification should be used.
The additional test methods shall be fully described and appropriate limits, sampling plans and
inspection levels specified.
4 Test and measurement procedure
4.1 General
The sectional and/or blank detail specification shall contain the tests to be made, which
measurements are to be made before and after each test or sub-group of tests and the
sequence in which they shall be carried out. The stages of each test shall be carried out in the
order written. The measuring conditions shall be the same for initial and final measurements.
If national specifications within any quality assessment system include methods other than
those specified in the above standards, they shall be fully described.
Limits given in all specifications are absolute limits. The principle to take measurement
uncertainty into account shall be applied (see IEC QC 001002-3, annex C).
4.2 Standard atmospheric conditions
4.2.1 Standard atmospheric conditions for testing
Unless otherwise specified, all tests and measurements shall be made under standard
atmospheric conditions for testing as given in 5.3 of IEC 60068-1:
– temperature: 15 °C to 35 °C;
– relative humidity: 25 % to 75 %;
– air pressure: 86 kPa to 106 kPa.
Before the measurements are made, the component shall be stored at the measuring
temperature for a time sufficient to allow the entire component to reach this temperature. The
period as prescribed for recovery at the end of a test is normally sufficient for this purpose.
When measurements are made at a temperature other than the specified temperature the results
shall, where necessary, be corrected to the specified temperature. The ambient temperature
during the measurements shall be stated in the test report. In the event of a dispute, the
measurements shall be repeated, using one of the referee temperatures (as given in 4.2.3) and
such other conditions as are prescribed in this specification.
When tests are conducted in a sequence, the final measurements of one test may be taken as
the initial measurements for the succeeding test.
During measurements the component shall not be exposed to draughts, direct sunlight or other
influences likely to cause errors.
– 14 – 60938-1 © IEC:1999(E)
4.2.2 Recovery conditions
Unless otherwise specified, recovery shall take place under the standard atmospheric
conditions for testing (4.2.1).
If recovery under closely controlled conditions is necessary, the controlled recovery conditions
of 5.4.1 of IEC 60068-1 shall be used.
Unless otherwise specified in the relevant specification, a duration of 1 h to 2 h shall be used.
4.2.3 Referee conditions
For referee purposes, one of the standard atmospheric conditions for referee tests taken
from 5.2 of IEC 60068-1, as given in table 1, shall be selected:
Table 1 – Reference test: standard atmospheric conditions
Temperature Relative Air pressure
humidity
°C kPa
%
20 ± 1 63 to 67 86 to 106
23 ± 1 48 to 52 86 to 106
25 ± 1 48 to 52 86 to 106
27 ± 1 63 to 67 86 to 106
4.2.4 Reference conditions
For reference purposes, the standard atmospheric conditions for reference given in 5.1 of
IEC 60068-1 apply:
– temperature: 20 °C;
– air pressure: 101,3 kPa.
4.3 Drying
Unless otherwise specified in the relevant specification, the inductor shall be conditioned for
96 h ± 4 h by heating in a circulating air oven at a temperature of 55 °C ± 2 °C and a relative
humidity not exceeding 20 %.
The inductor shall then be allowed to cool in a desiccator using a suitable desiccant, such as
activated alumina or silica gel, and shall be kept therein from the time of removal from the oven
to the beginning of the specified tests.
4.4 Visual examination and check of dimensions
4.4.1 Visual examination
The condition, workmanship and finish shall be satisfactory as checked by visual examination
(see 2.2.23).
Marking shall be legible, as checked by visual examination and shall conform to the
requirements of the detail specification.
4.4.2 Dimensions (gauging)
The dimensions indicated in the detail specification as being suitable for gauging shall be
checked, and shall comply with the values prescribed in the detail specification.
When applicable, measurements shall be made in accordance with IEC 60294.
60938-1 © IEC:1999(E) – 15 –
4.4.3 Dimensions (detail)
All dimensions prescribed in the detail specification shall be checked and shall comply with the
values prescribed.
4.4.4 Creepage distances and clearances
For main inductors, creepage distances and clearances on the outside of the inductor between
live parts of different polarity or between live parts and a metal case shall be not less than the
appropriate values given in the table 2.
Table 2 – Creepage distances and clearances
Rated voltage
U ≤ 130 V 130 V < U ≤ 250 V 250 V < U ≤ 500 V 500 V < U ≤ 760 V
R R R R
Point of
measurement
Creepage Clearance Creepage Clearance Creepage Clearance Creepage Clearance
distance distance distance distance
mm mm mm mm
mm mm mm mm
Between live 2,0 1,5 3,0 2,5 4,0 3,0 6,3 5,5
parts of different
polarity
Between live 2,0 1,5 4,0 3,0 6,3 5,5 6,3 5,5
parts and other
metal parts over
basic insulation
Between live 8,0 8,0 8,0 8,0
parts and other
metal parts over
reinforced
insulation
NOTE – The values are for basic insulation in accordance with clause 29 of IEC 60335-1.
Compliance shall be checked by measurement according to the rules laid down in IEC 60335-1
for measurement on the outside of the inductor. Additional requirements may be necessary, for
example for drip-proof or splash-proof inductors.
4.5 Insulation resistance
4.5.1 Unless otherwise specified in the relevant specification, the insulation resistance shall
be measured, at the d.c. voltage specified in table 3.
Table 3 – Measuring voltage
Voltage rating of inductor Measuring voltage
V V
UR or UC < 10 UC or UR ± 10 %
10 ≤ UR or UC < 100 10 ± 1 *
100 ≤ U or U < 500 100 ± 15
R C
500 ≤ U or U 500 ± 50
R C
* When it can be demonstrated that the voltage has no influence on
the measuring result, or that a known relationship exists, measure-
ment can be performed at voltages up to the rated or category
voltage (10 V shall be used in case of dispute).
– 16 – 60938-1 © IEC:1999(E)
U is the rated voltage for use in defining the measuring voltage to be used under standard
R
atmospheric conditions for testing.
U is the category voltage for use in defining the measuring voltage to be used at the upper
C
category temperature.
4.5.2 The insulation resistance shall be measured between the measuring points defined in
table 4, specified in the relevant specification.
Test A, between terminations, applies to all inductors, whether insulated or not.
Test B, internal insulation, applies to insulated inductors in uninsulated metal cases.
Test C, external insulation, applies to insulated inductors in non-metallic cases or in insulated
metal cases. For this test, the measuring voltage shall be applied using one of the three
following methods as specified in the relevant specification.
4.5.2.1 Foil method
A metal foil shall be closely wrapped around the body of the inductor. For inductors with axial
terminations this foil shall extend beyond each end by not less than 5 mm, provided that a
minimum distance of 1 mm can be maintained between the foil and the terminations. If this
minimum distance cannot be maintained, the extension of the foil shall be reduced by as much
as is necessary to establish the distance of 1 mm.
For inductors with unidirectional terminations a minimum distance of 1 mm shall be maintained
between the edge of the foil and each termination.
4.5.2.2 Method for inductors with mounting devices
The inductor shall be mounted in its normal manner on a metal plate, which extends at least
13 mm in all directions beyond the mounting face of the inductor.
4.5.2.3 V-block method
The inductor shall be clamped in the trough of 90° metallic V-block of such size that the
inductor body does not extend beyond the extremities of the block.
The clamping force shall be such as to guarantee adequate contact between the inductor and
the block. The clamping force is to be chosen in such a way that no destruction or damage of
the inductor occurs.
The inductor shall be positioned as follows:
a) for cylindrical inductors: the inductor shall be positioned in the block so that the termination
furthest from the axis of the inductor is nearest to one of the faces of the block;
b) for rectangular inductors: the inductor shall be positioned in the block so that the termination
nearest the edge of the inductor is nearest to one of the faces of the block.
For cylindrical and rectangular inductors having axial terminations, any out-of-centre
positioning of the termination at its emergence from the inductor body shall be ignored.
4.5.3 The insulation resistance shall be measured after the voltage has been applied for
60 s ± 5 s, unless otherwise prescribed in the detail specification.
60938-1 © IEC:1999(E) – 17 –
4.5.4 When prescribed by the detail specification, the temperature at which the measurement
is made shall be noted. If this temperature differs from 20 °C, a correction shall be made to the
measured value by multiplying the value by the appropriate correction factor prescribed in the
sectional specification.
4.5.5 The relevant specification shall prescribe:
a) the tests and the measuring voltage corresponding to each of these tests (see table 4);
b) the method of applying the voltage (one of the methods described in 4.5.2.1, 4.5.2.2 or
4.5.2.3);
c) time of electrification if other than 1 min;
d) any special precautions to be taken during measurements;
e) any correction factors required for measurement over the range of temperatures covered by
the standard atmospheric conditions for testing;
f) the temperature of measurement if other than the standard atmospheric conditions for
testing;
g) the minimum value of insulation resistance for the various tests (see table 4).
Table 4 – Measuring points
Tests Description
A Between terminations Between pairs of lines carrying the load current through
the suppression components for example line-line or
line-neutral*
B Internal insulation Between the load current terminations connected
together and the case (except where the case is one
termination) (metal cased types only)
C External insulation Between the load current terminations connected
together and the metal plate or foil (insulated cases not
employing metal)
or
Between case and metal plate foil (insulated metal cased
types only)
* Applies only to inductors with more than one winding.
– 18 – 60938-1 © IEC:1999(E)
EXAMPLE 1
1 3
Metal case
IEC 1469/99
Test A between 1 and 2 or 3 and 4.
Test B between 1, 2, 3, 4 together and 5.
EXAMPLE 2
Insulating case
2 4
IEC 1470/99
Test A between 1 and 2 or 3 and 4.
Test C between 1, 2, 3, 4 together and the metal foil 5 wrapped around the case.
4.6 Voltage proof
The test prescribed below is a d.c. test. When the relevant specification prescribes an a.c. test,
the test circuit shall be prescribed by that specification.
4.6.1 Test circuit (for the test between terminations)
The test circuit shall be such that the conditions relating to the charging and discharging
currents and the time constant for charging, prescribed in the relevant specification, are
complied with.
Figure 1 specifies the characteristics of a suitable test circuit.
60938-1 © IEC:1999(E) – 19 –
R
R
V
Inductor
C
s
under test
IEC 1471/99
Figure 1 – Voltage proof test circuit
The resistance of the voltmeter shall be not less than 10 000 Ω/V. The resistor R includes the
internal resistance of the d.c. supply. The resistors R and R shall have a value sufficient to
1 2
limit the charging and discharging current to the value prescribed in the relevant specification.
4.6.2 Test
Depending on the case, the test comprises one or more parts in accordance with table 4 and
the requirements of the relevant specification.
4.6.2.1 Test A – Between terminations
Test A of table 4, in accordance with the requirements of the relevant specification.
Procedure
With the switch in position 2, connect the two terminals at the top of the diagram to a variable
d.c. supply of sufficient power adjusted to the required test voltage.
Connect the inductor to be tested to the test circuit as indicated in the diagram.
Move the switch to position 1 to charge the stray capacitance C .
S
The switch shall remain in this position for the time specified after the test voltage has been
reached.
Discharge the stray capacitance C through R by moving the switch to position 2. As soon as
S 2
the voltmeter reading has fallen to zero, short-circuit the inductor by moving the switch to
position 3 and disconnect the inductor.
– 20 – 60938-1 © IEC:1999(E)
4.6.2.2 Test B – Internal insulation
Test B of table 4, in accordance with the requirements of the relevant specification.
Procedure
The specified test voltage is applied instantaneously via the internal resistance of the power
supply for the time specified in the relevant specification.
4.6.2.3 Test C – External insulation (applicable only to insulated inductors in non-metallic
case or in insulated metal case)
Test C of table 4, using one of the three following methods for the application of the voltage in
accordance with the requirements of the relevant specification.
Foil method
A metal foil shall be closely wrapped around the body of the inductor.
For inductors with axial terminations this foil shall extend beyond each end by not less than
5 mm, provided that a minimum distance of 1 mm/kV can be maintained between the foil and
the terminations. If this minimum cannot be maintained, the extension of the foil shall be
reduced by as much as is necessary to establish the distance of 1 mm/kV of test voltage.
For inductors with unidirectional terminations, a minimum distance of 1 mm/kV shall be
maintained between the edge of the foil and each termination.
In no case shall the distance between the foil and the terminations be less than 1 mm.
Method for inductors with mounting devices
The inductor shall be mounted in its normal manner on a metal plate which extends by not less
than 13 mm in all directions beyond the mounting face of the inductor.
V-block method
The inductor shall be clamped in the trough of a 90° metallic V-block of such size that the
inductor body does not extend beyond the extremities of the block.
The clamping force shall be such as to guarantee adequate contact between the inductor and
the block.
The inductor shall be positioned in accordance with the following:
a) for cylindrical inductors: the inductor shall be positioned in the block so that the termination
furthest from the axis of the capacitor is nearest to one of the faces of the block;
b) for rectangular inductors: the inductor is positioned in the block so that the termination
nearest the edge of the inductor is nearest to one of the faces of the block.
For cylindrical and rectangular inductors having axial terminations, any out-of-centre posi-
tioning of the termination at its emergence from the inductor body shall be ignored.
60938-1 © IEC:1999(E) – 21 –
Procedure
The specified test voltage is applied instantaneously through the internal resistance of the
power source for the time specified in the relevant specification.
4.6.3 Requirements
For each of the specified tests there shall be no sign of breakdown or flashover during the test
period.
4.6.4 Repeated application of the voltage proof test may cause permanent damage to the
inductor and should be avoided as far as possible.
4.6.5 The relevant specification shall prescribe:
a) the tests (see table 4) and the test voltage corresponding to each of these tests;
b) for the external insulation test (test C): the method of applying the test voltage (one of the
methods described in 4.6.2.3);
c) the time for which the voltage is applied;
d) the maximum charge and discharge currents.
4.7 Inductance
The inductance shall be measured and shall be within the declared tolerance of the rated
inductance. The measuring current or voltage and frequency shall be specified in the detail
specification.
As the measured value of the inductance may be a function of current, frequency and
temperature, these parameters shall be recorded in the test report and shall remain constant
throughout the test.
4.8 Insertion loss
The measurement method shall be selected from those described in CISPR 17.
4.9 Robustness of terminations
The inductors shall be subjected to tests Ua , Ub, Uc and Ud of IEC 60068-2-21, as applicable.
4.9.1 Test Ua – Tensile
...
INTERNATIONAL IEC
STANDARD 60938-1
QC 280000
Edition 2.1
2006-11
Edition 2:1999 consolidated with amendment 1:2006
Fixed inductors for electromagnetic
interference suppression –
Part 1:
Generic specification
Reference number
Publication numbering
As from 1 January 1997 all IEC publications are issued with a designation in the
60000 series. For example, IEC 34-1 is now referred to as IEC 60034-1.
Consolidated editions
The IEC is now publishing consolidated versions of its publications. For example,
edition numbers 1.0, 1.1 and 1.2 refer, respectively, to the base publication, the
base publication incorporating amendment 1 and the base publication incorporating
amendments 1 and 2.
Further information on IEC publications
The technical content of IEC publications is kept under constant review by the IEC,
thus ensuring that the content reflects current technology. Information relating to
this publication, including its validity, is available in the IEC Catalogue of
publications (see below) in addition to new editions, amendments and corrigenda.
Information on the subjects under consideration and work in progress undertaken
by the technical committee which has prepared this publication, as well as the list
of publications issued, is also available from the following:
• IEC Web Site (www.iec.ch)
• Catalogue of IEC publications
The on-line catalogue on the IEC web site (http://www.iec.ch/searchpub/cur_fut.htm)
enables you to search by a variety of criteria including text searches, technical
committees and date of publication. On-line information is also available on
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• IEC Just Published
This summary of recently issued publications (http://www.iec.ch/online_news/
justpub/jp_entry.htm) is also available by email. Please contact the Customer
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If you have any questions regarding this publication or need further assistance,
please contact the Customer Service Centre:
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Fax: +41 22 919 03 00
INTERNATIONAL IEC
STANDARD 60938-1
QC 280000
Edition 2.1
2006-11
Edition 2:1999 consolidated with amendment 1:2006
Fixed inductors for electromagnetic
interference suppression –
Part 1:
Generic specification
© IEC 2006 ⎯ Copyright - all rights reserved
No part of this publication may be reproduced or utilized in any form or by any means, electronic or
mechanical, including photocopying and microfilm, without permission in writing from the publisher.
International Electrotechnical Commission, 3, rue de Varembé, PO Box 131, CH-1211 Geneva 20, Switzerland
Telephone: +41 22 919 02 11 Telefax: +41 22 919 03 00 E-mail: inmail@iec.ch Web: www.iec.ch
PRICE CODE
CL
Commission Electrotechnique Internationale
International Electrotechnical Commission
МеждународнаяЭлектротехническаяКомиссия
For price, see current catalogue
– 2 – 60938-1 © IEC:1999+A1:2006(E)
CONTENTS
FOREWORD.4
1 General.6
1.1 Scope.6
1.2 Normative references.6
2 Technical data .8
2.1 Units and symbols .8
2.2 Definitions.8
2.3 Preferred values .11
2.4 Marking.11
3 Quality assessment procedures .11
3.1 General.11
3.2 Primary stage of manufacture .11
3.3 Structurally similar inductors .11
3.4 Qualification approval procedures .11
3.5 Quality conformance inspection .12
3.6 Alternative test methods .12
3.7 Unchecked parameters.13
4 Test and measurement procedure.13
4.1 General.13
4.2 Standard atmospheric conditions .13
4.3 Drying.14
4.4 Visual examination and check of dimensions.14
4.5 Insulation resistance.16
4.6 Voltage proof.18
4.7 Inductance.21
4.8 Insertion loss .21
4.9 Robustness of terminations.21
4.10 Resistance to soldering heat.22
4.11 Solderability (applicable only for terminations intended to be soldered).23
4.12 Rapid change of temperature.23
4.13 Vibration.24
4.14 Bump.24
4.15 Shock.24
4.16 Container sealing.24
4.17 Climatic sequence .25
4.18 Damp heat, steady state .26
4.19 Temperature rise.26
4.20 Endurance.27
4.21 Passive flammability .27
4.22 Active flammability.28
4.23 Solvent resistance of marking .28
4.24 Component solvent resistance .28
60938-1 © IEC:1999+A1:2006(E) – 3 –
Annex A (normative) Interpretation of sampling plans and procedures as described
in IEC 60410 for use within the IEC quality assessment system
for electronic components (IECQ).29
Annex B (normative) Rules for the preparation of detail specifications for capacitors
and resistors for electronic equipment .30
Annex C (normative) Requirements for earth inductors.31
Figure 1 – Voltage proof test circuit .19
Table 1 – Reference test: standard atmospheric conditions .14
Table 2 – Creepage distances and clearances.15
Table 3 – Measuring voltage .16
Table 4 – Measuring points .17
Table 5 – Force.22
Table 6 – Torque.22
Table 7 – Number of cycles .26
Table 8 – Severities and requirements.28
Table C.1 – Rated current related to minimum cross-sectional area of copper lead (mm )
of the earth inductor .31
– 4 – 60938-1 © IEC:1999+A1:2006(E)
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
FIXED INDUCTORS FOR ELECTROMAGNETIC
INTERFERENCE SUPPRESSION –
Part 1: Generic specification
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with an IEC Publication.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 60938-1 has been prepared by IEC technical committee 40:
Capacitors and resistors for electronic equipment.
This consolidated version of IEC 60938-1 consists of the second edition (1999) [documents
40/1110/FDIS and 40/1136/RVD] and its amendment 1 (2006) [documents 40/1602/CDV and
40/1699A/RVC].
The technical content is therefore identical to the base edition and its amendment and has
been prepared for user convenience.
It bears the edition number 2.1.
A vertical line in the margin shows where the base publication has been modified by
amendment 1.
The QC number that appears on the front cover of this publication is the specification number
in the IEC Quality Assessment System for Electronic Components (IECQ).
60938-1 © IEC:1999+A1:2006(E) – 5 –
Annexes A, B and C form an integral part of this standard.
The committee has decided that the contents of the base publication and its amendments will
remain unchanged until the maintenance result date indicated on the IEC web site under
"http://webstore.iec.ch" in the data related to the specific publication. At this date,
the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
A bilingual version of this publication may be issued at a later date.
– 6 – 60938-1 © IEC:1999+A1:2006(E)
FIXED INDUCTORS FOR ELECTROMAGNETIC
INTERFERENCE SUPPRESSION –
Part 1: Generic specification
1 General
1.1 Scope
This International Standard applies to inductors designed for electromagnetic interference
suppression intended for use within, or associated with, electronic or electrical equipment and
machines. It is restricted to inductors for which safety tests are appropriate.
The combination of two or more inductors within one enclosure is also included.
Inductors within the scope of this standard may also be used to protect apparatus and
machines from electrical noise and voltage or current transients coming from either the supply
or from other parts of the apparatus.
This standard does not necessarily apply in its entirety to inductors intended for use on motor
vehicles, in aircraft or for marine applications.
1.2 Normative references
The following referenced documents are indispensable for the application of this document. For
dated references, only the edition cited applies. For undated references, the latest edition of
the referenced document (including any amendments) applies.
IEC 60027 (all parts), Letter symbols to be used in electrical technology
IEC 60050 (all parts), International Electrotechnical Vocabulary (IEV)
IEC 60062:1992, Marking codes for resistors and capacitors
IEC 60068-1:1988, Environmental testing – Part 1: General and guidance
Amendment 1 (1992)
IEC 60068-2-1:1990, Environmental testing – Part 2: Tests – Tests A: Cold
Amendment 1 (1993)
Amendment 2 (1994)
IEC 60068-2-2:1974, Environmental testing – Part 2: Tests – Tests B: Dry Heat
Amendment 1 (1993)
Amendment 2 (1994)
IEC 60068-2-3:1969, Environmental testing – Part 2: Tests – Test Ca: Damp heat, steady state
Amendment 1 (1984)
IEC 60068-2-6:1995, Environmental testing – Part 2: Tests – Test Fc: Vibration (sinusoidal)
IEC 60068-2-13:1983, Environmental testing – Part 2: Tests – Test M: Low air pressure
60938-1 © IEC:1999+A1:2006(E) – 7 –
IEC 60068-2-14:1984, Environmental testing – Part 2: Tests – Test N: Change of temperature
Amendment 1 (1986)
IEC 60068-2-17:1994, Environmental testing – Part 2: Tests – Test Q: Sealing
IEC 60068-2-20:1979, Environmental testing – Part 2: Tests – Test T: Soldering
Amendment 2 (1987)
IEC 60068-2-21:1983, Environmental testing – Part 2: Tests – Test U: Robustness of
terminations and integral mounting devices
Amendment 2 (1991)
Amendment 3 (1992)
IEC 60068-2-27:1987, Environmental testing – Part 2: Tests – Test Ea and guidance: Shock
IEC 60068-2-29:1987, Environmental testing – Part 2: Tests – Test Eb and guidance: Bump
IEC 60068-2-30:1980, Environmental testing – Part 2: Tests – Test Db and guidance: Damp
heat, cyclic (12 + 12 hour cycle)
Amendment 1 (1985)
IEC 60068-2-45:1980, Environmental testing – Part 2: Tests – Test XA and guidance:
Immersion in cleaning solvents
Amendment 1 (1993)
IEC 60294:1969, Measurement of the dimensions of a cylindrical component having two axial
terminations
IEC 60335-1:1991, Safety of household and similar electrical appliances – Part 1: General
requirements
IEC 60410:1973, Sampling plans and procedures for inspection by attributes
IEC 60617 (all parts), Graphical symbols for diagrams
IEC 60695-2-2:1991, Fire hazard testing – Section 2: Needle-flame test
Amendment 1 (1994)
CISPR 17:1981, Methods of measurement of the suppression characteristics of passive radio
interference filters and suppression components
IEC QC 001002-3:1998, Rules of Procedure of the IEC Quality Assessment System for Electronic
Components (IECQ) – Part 3: Approval procedures
ISO 1000:1992, SI units and recommendations for the use of their multiples and of certain
other units
– 8 – 60938-1 © IEC:1999+A1:2006(E)
2 Technical data
2.1 Units and symbols
Units, graphical symbols, letter symbols and terminology shall, whenever possible, be taken
from the following publications:
IEC 60027
IEC 60050
IEC 60617
ISO 1000
When further items are required they shall be derived in accordance with the principles of the
documents listed above.
2.2 Definitions
For the purpose of this International Standard, the following definitions apply.
2.2.1
type
a group of components having similar design features and the similarity of whose
manufacturing techniques enables them to be grouped together either for qualification approval
or for quality conformance inspection
They are generally covered by a single detail specification.
NOTE Components described in several detail specifications, may, in some cases, be considered as belonging to
the same type.
2.2.2
style
a sub-division of a type, generally based on dimensional factors.
A style may include several variants, generally of a mechanical order
2.2.3
family (of electronic components)
a group of electronic components which predominantly displays a particular physical attribute
and/or fulfils a defined function
2.2.4
sub-family (of electronic components)
a group of components within a family manufactured by similar technological methods
2.2.5
rated voltage (U )
R
rated voltage is either the maximum r.m.s. operating voltage of rated frequency or the
maximum d.c. operating voltage which may be applied continuously to the terminations of the
inductor at any temperature between the lower category temperature and the rated temperature
NOTE For inductors with only one winding, the rated voltage should only be applied between one terminal and any
conducting surface with which the case is liable to come into contact in normal use. For inductors having more than
one winding, the rated voltage may be applied across two individual windings.
60938-1 © IEC:1999+A1:2006(E) – 9 –
2.2.6
category voltage (U )
C
maximum voltage which may be applied continuously to an inductor at its upper category
temperature
2.2.7
lower category temperature
minimum external surface temperature for which the inductor has been designed to operate
continuously
2.2.8
upper category temperature
maximum external surface temperature for which the inductor has been designed to operate
continuously
NOTE The external surface temperature can be affected by internal heating due to the lead-through current. The
terminations are considered to be part of the external surface.
2.2.9
rated temperature
maximum ambient temperature at which an inductor can carry its rated current
2.2.10
rated current
maximum r.m.s. operating current at rated frequency or maximum d.c. operating current which
allows continuous operation of the inductor at the rated temperature. It is assigned by the
manufacturer for one or both of the following conditions:
a) free air (I );
RO
b) with a specified heat sink (I ).
RH
2.2.11
rated inductance (L )
R
inductance value for which the inductor has been designed and which is usually indicated upon it
2.2.12
insertion loss
ratio of the voltage before and after the insertion of the suppressor in the circuit as measured
at the terminations
NOTE 1 The insertion loss can be measured either with a symmetrical or an asymmetrical test circuit.
NOTE 2 When expressed in decibels the insertion loss is 20 times the logarithm of the ratio stated.
2.2.13
asymmetrical test circuit
a test circuit in which the inductor under test is connected with a coaxial cable of which the
outer conductor constitutes a return path for high-frequency current
[CISPR 17:1981, 3.5 modified]
2.2.14
symmetrical test circuit
a test circuit in which the inductor under test is connected with screened conductor pairs in
which the asymmetrical voltage is small enough to be neglected
[CISPR 17:1981, 3.6 modified]
– 10 – 60938-1 © IEC:1999+A1:2006(E)
2.2.15
insulated inductor
an inductor in which all terminations connected to a section may be raised to a potential
different (but not less than the rated voltage) from that of any conducting surface with which
the case is liable to come into contact in normal use
2.2.16
uninsulated inductor
an inductor in which at least one of the terminations connected to a section cannot be raised to
a potential different (but not less than the rated voltage) from that of any conducting surface
with which the case is liable to come into contact in normal use
2.2.17
electromagnetic interference suppression inductor
an inductor which at mains frequency has a low impedance, but which at radio frequency has a
high inductive impedance
NOTE 1 It may be used for reducing the interference at frequencies caused by electrical equipment.
NOTE 2 These inductors are sometimes known as RF chokes.
2.2.18
current-compensated inductor
an inductor having more than one winding on a single core arranged in such a way that the
resultant magnetization caused by the current is near zero
2.2.19
earth inductor
an inductor connected in the earth lead of an equipment.
For requirements for earth inductors, see annex C
2.2.20
thyristor inductor
an inductor used in thyristor controlled circuits
2.2.21
mains inductor
an inductor intended for direct electrical connection to the supply mains
NOTE This inductor may form part of an equipment.
2.2.22
TV choke
an inductor designed to reduce interference mainly in the frequency range 30 MHz to 300 MHz
NOTE Unencapsulated, non-current compensated TV chokes are not within the scope of this specification, but
should be considered as part of the equipment wiring.
2.2.23
visible damage
visible damage which reduces the usability of the inductor unit for intended purpose
60938-1 © IEC:1999+A1:2006(E) – 11 –
2.3 Preferred values
Each sectional specification shall prescribe the preferred values appropriate to the sub-family
covered by that sectional specification.
2.4 Marking
2.4.1 General
The sectional specification shall indicate the identification criteria and other information to be
shown on the inductors and the packing.
The order of priority for marking small inductors shall be specified.
2.4.2 Coding
When coding is used for tolerance or date of manufacture, the method shall be selected from
those given in IEC 60062.
3 Quality assessment procedures
3.1 General
When these standards are used for the purpose of a full quality assessment system such
as the IEC Quality Assessment System for Electronic Components (IECQ), compliance to 3.4
or 3.5 is required.
When these standards are used outside quality assessment systems for purposes such as
design proving or type testing, the procedures and requirements of 3.4.1 and 3.4.3 may be
used, but the tests and parts of tests shall be applied in the order given in the test schedules.
Before inductors can be qualified according to the procedures of this clause the manufacturer shall
obtain the approval of his organization in accordance with the provisions of IEC QC 001002-3.
For certification by an independent test laboratory the procedure of 3.4.3 shall be sufficient,
except that the test laboratory will produce the evidence of conformance.
3.2 Primary stage of manufacture
The primary stage of manufacture is the winding of the inductive element(s).
3.3 Structurally similar inductors
The grouping of structurally similar inductors for the purpose of qualification approval and
quality conformance inspection shall be prescribed in the sectional specification.
3.4 Qualification approval procedures
3.4.1 Eligibility for qualification approval
The manufacturer shall comply with 3.1.1 of IEC QC 001002-3.
3.4.2 Application for qualification approval
The manufacturer shall comply with 3.1.3 of IEC QC 001002-3.
– 12 – 60938-1 © IEC:1999+A1:2006(E)
3.4.3 Test procedure for qualification approval
In addition to the requirements of 3.4.1 and 3.4.2, the manufacturer shall produce test evidence
to show conformance to the specification requirements on the fixed sample size test schedule
given in the sectional specification.
The specimens taken to form the sample shall be selected at random from current production
or as agreed with the National Supervising Inspectorate (NSI).
3.4.4 Granting of qualification approval
Qualification approval shall be granted when the procedures in accordance with 3.1.4 of
IEC QC 001002-3 have been completed satisfactorily.
3.4.5 Maintenance of qualification approval
Qualification approval obtained as part of a quality assessment system shall be maintained by
regular demonstration of compliance with the requirements for quality conformance (see 3.5).
3.5 Quality conformance inspection
The blank detail specification(s) associated with the sectional specification shall prescribe the
test schedule for quality conformance inspection. This schedule shall also specify the grouping,
sampling and periodicity for the lot-by-lot and periodic inspection.
Operation of the switching rule for reduced inspection in group C is permitted in all sub-groups
except endurance. Sampling plans and inspection levels shall be selected from those given
in IEC 60410.
If required, more than one schedule may be specified.
3.5.1 Certified test records of released lots
When certified test records are requested by a purchaser, they shall be specified in the detail
specification.
3.5.2 Delayed delivery
Inductors held for a period exceeding three years (unless otherwise specified in the detail
specification) following the release of the lot shall, before delivery, be re-examined as specified
in the sectional specification.
Once a lot has been satisfactorily re-inspected, its quality is re-assured for three years from the
date of re-inspection.
3.5.3 Release for delivery before the completion of group B tests
When the conditions of IEC 60410 for changing to reduced inspection have been satisfied for
all group B tests, the manufacturer is permitted to release components before the completion
of such tests.
3.6 Alternative test methods
See 3.2.3.7 of IEC QC 001002-3 with the following details:
In case of dispute, for referee and reference purposes only the specified methods shall be used.
60938-1 © IEC:1999+A1:2006(E) – 13 –
3.7 Unchecked parameters
Only those parameters of a component which have been specified in a detail specification and
which are subject to testing can be assumed to be within the specified limits.
It cannot be assumed that any unspecified parameter will remain unchanged from one
component to another. Should it be necessary, for any reason, for further parameters to be
controlled, then a new, more extensive specification should be used.
The additional test methods shall be fully described and appropriate limits, sampling plans and
inspection levels specified.
4 Test and measurement procedure
4.1 General
The sectional and/or blank detail specification shall contain the tests to be made, which
measurements are to be made before and after each test or sub-group of tests and the
sequence in which they shall be carried out. The stages of each test shall be carried out in the
order written. The measuring conditions shall be the same for initial and final measurements.
If national specifications within any quality assessment system include methods other than
those specified in the above standards, they shall be fully described.
Limits given in all specifications are absolute limits. The principle to take measurement
uncertainty into account shall be applied (see IEC QC 001002-3, annex C).
4.2 Standard atmospheric conditions
4.2.1 Standard atmospheric conditions for testing
Unless otherwise specified, all tests and measurements shall be made under standard
atmospheric conditions for testing as given in 5.3 of IEC 60068-1:
– temperature: 15 °C to 35 °C;
– relative humidity: 25 % to 75 %;
– air pressure: 86 kPa to 106 kPa.
Before the measurements are made, the component shall be stored at the measuring
temperature for a time sufficient to allow the entire component to reach this temperature. The
period as prescribed for recovery at the end of a test is normally sufficient for this purpose.
When measurements are made at a temperature other than the specified temperature the results
shall, where necessary, be corrected to the specified temperature. The ambient temperature
during the measurements shall be stated in the test report. In the event of a dispute, the
measurements shall be repeated, using one of the referee temperatures (as given in 4.2.3) and
such other conditions as are prescribed in this specification.
When tests are conducted in a sequence, the final measurements of one test may be taken as
the initial measurements for the succeeding test.
During measurements the component shall not be exposed to draughts, direct sunlight or other
influences likely to cause errors.
– 14 – 60938-1 © IEC:1999+A1:2006(E)
4.2.2 Recovery conditions
Unless otherwise specified, recovery shall take place under the standard atmospheric
conditions for testing (4.2.1).
If recovery under closely controlled conditions is necessary, the controlled recovery conditions
of 5.4.1 of IEC 60068-1 shall be used.
Unless otherwise specified in the relevant specification, a duration of 1 h to 2 h shall be used.
4.2.3 Referee conditions
For referee purposes, one of the standard atmospheric conditions for referee tests taken
from 5.2 of IEC 60068-1, as given in table 1, shall be selected:
Table 1 – Reference test: standard atmospheric conditions
Temperature Relative Air pressure
humidity
°C % kPa
20 ± 1 63 to 67 86 to 106
23 ± 1 48 to 52 86 to 106
25 ± 1 48 to 52 86 to 106
27 ± 1 63 to 67 86 to 106
4.2.4 Reference conditions
For reference purposes, the standard atmospheric conditions for reference given in 5.1 of
IEC 60068-1 apply:
– temperature: 20 °C;
– air pressure: 101,3 kPa.
4.3 Drying
Unless otherwise specified in the relevant specification, the inductor shall be conditioned for
96 h ± 4 h by heating in a circulating air oven at a temperature of 55 °C ± 2 °C and a relative
humidity not exceeding 20 %.
The inductor shall then be allowed to cool in a desiccator using a suitable desiccant, such as
activated alumina or silica gel, and shall be kept therein from the time of removal from the oven
to the beginning of the specified tests.
4.4 Visual examination and check of dimensions
4.4.1 Visual examination
The condition, workmanship and finish shall be satisfactory as checked by visual examination
(see 2.2.23).
Marking shall be legible, as checked by visual examination and shall conform to the
requirements of the detail specification.
60938-1 © IEC:1999+A1:2006(E) – 15 –
4.4.2 Dimensions (gauging)
The dimensions indicated in the detail specification as being suitable for gauging shall be
checked, and shall comply with the values prescribed in the detail specification.
When applicable, measurements shall be made in accordance with IEC 60294.
4.4.3 Dimensions (detail)
All dimensions prescribed in the detail specification shall be checked and shall comply with the
values prescribed.
4.4.4 Creepage distances and clearances
For main inductors, creepage distances and clearances on the outside of the inductor between
live parts of different polarity or between live parts and a metal case shall be not less than the
appropriate values given in the table 2.
Table 2 – Creepage distances and clearances
Rated voltage
U ≤ 130 V 130 V < U ≤ 250 V 250 V < U ≤ 500 V 500 V < U ≤ 760 V
R R R R
Point of
measurement
Creepage Clearance Creepage Clearance Creepage Clearance Creepage Clearance
distance distance distance distance
mm mm mm mm mm mm mm mm
Between live 2,0 1,5 3,0 2,5 4,0 3,0 6,3 5,5
parts of different
polarity
Between live 2,0 1,5 4,0 3,0 6,3 5,5 6,3 5,5
parts and other
metal parts over
basic insulation
Between live 8,0 8,0 8,0 8,0
parts and other
metal parts over
reinforced
insulation
NOTE The values are for basic insulation in accordance with clause 29 of IEC 60335-1.
Compliance shall be checked by measurement according to the rules laid down in IEC 60335-1
for measurement on the outside of the inductor. Additional requirements may be necessary, for
example for drip-proof or splash-proof inductors.
– 16 – 60938-1 © IEC:1999+A1:2006(E)
4.5 Insulation resistance
4.5.1 Unless otherwise specified in the relevant specification, the insulation resistance shall
be measured, at the d.c. voltage specified in table 3.
Table 3 – Measuring voltage
Voltage rating of inductor Measuring voltage
V V
U or U < 10 U or U ± 10 %
R C C R
10 ≤ U or U < 100 10 ± 1 *
R C
100 ≤ U or U < 500 100 ± 15
R C
500 ≤ U or U 500 ± 50
R C
* When it can be demonstrated that the voltage has no influence on
the measuring result, or that a known relationship exists, measure-
ment can be performed at voltages up to the rated or category
voltage (10 V shall be used in case of dispute).
U is the rated voltage for use in defining the measuring voltage to be used under standard
R
atmospheric conditions for testing.
U is the category voltage for use in defining the measuring voltage to be used at the upper
C
category temperature.
4.5.2 The insulation resistance shall be measured between the measuring points defined in
table 4, specified in the relevant specification.
Test A, between terminations, applies to all inductors, whether insulated or not.
Test B, internal insulation, applies to insulated inductors in uninsulated metal cases.
Test C, external insulation, applies to insulated inductors in non-metallic cases or in insulated
metal cases. For this test, the measuring voltage shall be applied using one of the three
following methods as specified in the relevant specification.
4.5.2.1 Foil method
A metal foil shall be closely wrapped around the body of the inductor. For inductors with axial
terminations this foil shall extend beyond each end by not less than 5 mm, provided that a
minimum distance of 1 mm can be maintained between the foil and the terminations. If this
minimum distance cannot be maintained, the extension of the foil shall be reduced by as much
as is necessary to establish the distance of 1 mm.
For inductors with unidirectional terminations a minimum distance of 1 mm shall be maintained
between the edge of the foil and each termination.
4.5.2.2 Method for inductors with mounting devices
The inductor shall be mounted in its normal manner on a metal plate, which extends at least
13 mm in all directions beyond the mounting face of the inductor.
60938-1 © IEC:1999+A1:2006(E) – 17 –
4.5.2.3 V-block method
The inductor shall be clamped in the trough of 90° metallic V-block of such size that the
inductor body does not extend beyond the extremities of the block.
The clamping force shall be such as to guarantee adequate contact between the inductor and
the block. The clamping force is to be chosen in such a way that no destruction or damage of
the inductor occurs.
The inductor shall be positioned as follows:
a) for cylindrical inductors: the inductor shall be positioned in the block so that the termination
furthest from the axis of the inductor is nearest to one of the faces of the block;
b) for rectangular inductors: the inductor shall be positioned in the block so that the termination
nearest the edge of the inductor is nearest to one of the faces of the block.
For cylindrical and rectangular inductors having axial terminations, any out-of-centre
positioning of the termination at its emergence from the inductor body shall be ignored.
4.5.3 The insulation resistance shall be measured after the voltage has been applied for
60 s ± 5 s, unless otherwise prescribed in the detail specification.
4.5.4 When prescribed by the detail specification, the temperature at which the measurement
is made shall be noted. If this temperature differs from 20 °C, a correction shall be made to the
measured value by multiplying the value by the appropriate correction factor prescribed in the
sectional specification.
4.5.5 The relevant specification shall prescribe:
a) the tests and the measuring voltage corresponding to each of these tests (see table 4);
b) the method of applying the voltage (one of the methods described in 4.5.2.1, 4.5.2.2 or
4.5.2.3);
c) time of electrification if other than 1 min;
d) any special precautions to be taken during measurements;
e) any correction factors required for measurement over the range of temperatures covered by
the standard atmospheric conditions for testing;
f) the temperature of measurement if other than the standard atmospheric conditions for testing;
g) the minimum value of insulation resistance for the various tests (see table 4).
Table 4 – Measuring points
Tests Description
A Between terminations Between pairs of lines carrying the load current through the suppression
components; for example, line-line or line-neutral*
B Internal insulation Between the load-current terminations connected together and the case (except
where the case is one termination) (metal-cased types only)
C External insulation Between the load-current terminations connected together and the metal plate
or foil (insulated cases not employing metal)
or
Between the case and the metal plate foil (insulated metal-cased types only)
D Between windings and core Between hot-wired terminations and the core, if it is not insulated and
accessible
* Applies only to inductors with more than one winding.
– 18 – 60938-1 © IEC:1999+A1:2006(E)
EXAMPLE 1
1 3
Metal case
2 4
IEC 1469/99
Test A between 1 and
2 or 3 and 4.
Test B between 1, 2, 3, 4 together and 5.
EXAMPLE 2
Insulating case
2 4
IEC 1470/99
Test A between 1 and 2 or 3 and 4.
Test C between 1, 2, 3, 4 together and the metal foil 5 wrapped around the case.
4.6 Voltage proof
The test prescribed below is a d.c. test. When the relevant specification prescribes an a.c. test,
the test circuit shall be prescribed by that specification.
4.6.1 Test circuit (for the test between terminations)
The test circuit shall be such that the conditions relating to the charging and discharging
currents and the time constant for charging, prescribed in the relevant specification, are
complied with.
Figure 1 specifies the characteristics of a suitable test circuit.
60938-1 © IEC:1999+A1:2006(E) – 19 –
R
R
V
Inductor
C
s
under test
IEC 1471/99
Figure 1 – Voltage proof test circuit
The resistance of the voltmeter shall be not less than 10 000 Ω/V. The resistor R includes the
internal resistance of the d.c. supply. The resistors R and R shall have a value sufficient to
1 2
limit the charging and discharging current to the value prescribed in the relevant specification.
4.6.2 Test
Depending on the case, the test comprises one or more parts in accordance with table 4 and
the requirements of the relevant specification.
4.6.2.1 Test A – Between terminations
Test A of table 4, in accordance with the requirements of the relevant specification.
Procedure
With the switch in position 2, connect the two terminals at the top of the diagram to a variable
d.c. supply of sufficient power adjusted to the required test voltage.
Connect the inductor to be tested to the test circuit as indicated in the diagram.
Move the switch to position 1 to charge the stray capacitance C .
S
The switch shall remain in this position for the time specified after the test voltage has been
reached.
Discharge the stray capacitance C through R by moving the switch to position 2. As soon as
S 2
the voltmeter reading has fallen to zero, short-circuit the inductor by moving the switch to
position 3 and disconnect the inductor.
– 20 – 60938-1 © IEC:1999+A1:2006(E)
4.6.2.2 Test B – Internal insulation
Test B of table 4, in accordance with the requirements of the relevant specification.
Procedure
The specified test voltage is applied instantaneously via the internal resistance of the power
supply for the time specified in the relevant specification.
...
IEC 60938-1
Edition 2.0 1999-10
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
QC 280000
Fixed inductors for electromagnetic interference suppression –
Part 1: Generic specification
Inductances fixes d'antiparasitage –
Partie 1: Spécification générique
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IEC 60938-1
Edition 2.0 1999-10
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
QC 280000
Fixed inductors for electromagnetic interference suppression –
Part 1: Generic specification
Inductances fixes d'antiparasitage –
Partie 1: Spécification générique
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
V
CODE PRIX
ICS 29.100.10; 31.020 ISBN 2-8318-9863-3
– 2 – 60938-1 © IEC:1999
CONTENTS
FOREWORD.5
1 General .7
1.1 Scope.7
1.2 Normative references .7
2 Technical data .9
2.1 Units and symbols .9
2.2 Definitions .9
2.3 Preferred values .11
2.4 Marking .11
2.4.1 General .11
2.4.2 Coding.12
3 Quality assessment procedures .12
3.1 General .12
3.2 Primary stage of manufacture .12
3.3 Structurally similar inductors .12
3.4 Qualification approval procedures .12
3.4.1 Eligibility for qualification approval.12
3.4.2 Application for qualification approval .12
3.4.3 Test procedure for qualification approval.12
3.4.4 Granting of qualification approval .12
3.4.5 Maintenance of qualification approval.13
3.5 Quality conformance inspection .13
3.5.1 Certified test records of released lots .13
3.5.2 Delayed delivery .13
3.5.3 Release for delivery before the completion of group B tests.13
3.6 Alternative test methods .13
3.7 Unchecked parameters.13
4 Test and measurement procedure.14
4.1 General .14
4.2 Standard atmospheric conditions .14
4.2.1 Standard atmospheric conditions for testing .14
4.2.2 Recovery conditions.14
4.2.3 Referee conditions.14
4.2.4 Reference conditions .15
4.3 Drying.15
4.4 Visual examination and check of dimensions.15
4.4.1 Visual examination.15
4.4.2 Dimensions (gauging) .15
4.4.3 Dimensions (detail) .15
4.4.4 Creepage distances and clearances.15
4.5 Insulation resistance.16
4.6 Voltage proof.19
4.6.1 Test circuit (for the test between terminations) .19
4.6.2 Test.20
4.6.3 Requirements .22
4.7 Inductance.22
4.8 Insertion loss .22
60938-1 © IEC:1999 – 3–
4.9 Robustness of terminations.22
4.9.1 Test Ua – Tensile .22
4.9.2 Test Ub – Bending (first half of the sample).23
4.9.3 Test Uc – Torsion (second half of the sample).23
4.9.4 Test Ud – Torque (for terminations with threaded studs or screws and
for integral mounting devices) .23
4.9.5 Visual examination.23
4.10 Resistance to soldering heat.23
4.11 Solderability (applicable only for terminations intended to be soldered).24
4.12 Rapid change of temperature.24
4.13 Vibration.25
4.14 Bump .25
4.15 Shock.25
4.16 Container sealing.25
4.17 Climatic sequence .25
4.17.1 Initial measurements.26
4.17.2 Dry heat.26
4.17.3 Damp heat, cyclic, test Db, first cycle .26
4.17.4 Cold.26
4.17.5 Low air pressure .26
4.17.6 Damp heat, cyclic, test Db, remaining cycles .27
4.17.7 Final measurements .27
4.18 Damp heat, steady state .27
4.19 Temperature rise .27
4.20 Endurance.28
4.21 Passive flammability .28
4.22 Active flammability.29
4.23 Solvent resistance of marking .29
4.24 Component solvent resistance .29
4.24.1 Initial measurements.29
Annex A (normative) Interpretation of sampling plans and procedures as described in
IEC 60410 for use within the IEC quality assessment system for electronic components
(IECQ) .30
Annex B (normative) Rules for the preparation of detail specifications for capacitors
and resistors for electronic equipment .31
Annex C (normative) Requirements for earth inductors .32
Figure 1 – Voltage proof test circuit .20
– 4 – 60938-1 © IEC:1999
Table 1 – Reference test: standard atmospheric conditions .15
Table 2 – Creepage distances and clearances.16
Table 3 – Measuring voltage .16
Table 4 – Measuring points .18
Table 5 – Force.23
Table 6 – Torque.23
Table 7 – Number of cycles .27
Table 8 – Severities and requirements.29
Table C.1 – Rated current related to minimum cross-sectional area of copper lead
(mm ) of the earth inductor .32
60938-1 © IEC:1999 – 5–
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
FIXED INDUCTORS FOR ELECTROMAGNETIC
INTERFERENCE SUPPRESSION –
Part 1: Generic specification
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with an IEC Publication.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 60938-1 has been prepared by IEC technical committee 40:
Capacitors and resistors for electronic equipment.
This second edition cancels and replaces the first edition published in 1988 and constitutes a
minor revision related to tables, figures and references. It also includes Amendment 1 (2006).
This bilingual version, published in 2008-08, corresponds to the English version.
– 6 – 60938-1 © IEC:1999
The text of this standard is based on the following documents:
FDIS Report on voting
40/1110/FDIS 40/1136/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
The French version of this standard has not been voted upon.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all parts of the IEC 60938 series, under the general title: Fixed inductors for
electromagnetic interference suppression, can be found on the IEC website.
The QC number that appears on the front cover of this publication is the specification number
in the IEC quality assessment system for electronic components (IECQ).
The committee has decided that the contents of this publication will remain unchanged until the
maintenance result date indicated on the IEC web site under "http://webstore.iec.ch" in the data
related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
60938-1 © IEC:1999 – 7–
FIXED INDUCTORS FOR ELECTROMAGNETIC
INTERFERENCE SUPPRESSION –
Part 1: Generic specification
1 General
1.1 Scope
This International Standard applies to inductors designed for electromagnetic interference
suppression intended for use within, or associated with, electronic or electrical equipment and
machines. It is restricted to inductors for which safety tests are appropriate.
The combination of two or more inductors within one enclosure is also included.
Inductors within the scope of this standard may also be used to protect apparatus and
machines from electrical noise and voltage or current transients coming from either the supply
or from other parts of the apparatus.
This standard does not necessarily apply in its entirety to inductors intended for use on motor
vehicles, in aircraft or for marine applications.
1.2 Normative references
The following referenced documents are indispensable for the application of this document. For
dated references, only the edition cited applies. For undated references, the latest edition of
the referenced document (including any amendments) applies.
IEC 60027 (all parts), Letter symbols to be used in electrical technology
IEC 60050 (all parts), International Electrotechnical Vocabulary (IEV)
)
IEC 60062:1992 , Marking codes for resistors and capacitors
IEC 60068-1:1988, Environmental testing – Part 1: General and guidance
Amendment 1 (1992)
1)
IEC 60068-2-1:1990 , Environmental testing – Part 2: Tests – Tests A: Cold
Amendment 1 (1993)
Amendment 2 (1994)
1)
IEC 60068-2-2:1974 , Basic environmental testing procedures – Part 2: Tests – Tests B: Dry
Heat
Amendment 1 (1993)
Amendment 2 (1994)
)
IEC 60068-2-3 :1969, Basic environmental testing procedures – Part 2: Tests – Test Ca:
Damp heat, steady state
Amendment 1 (1984)
___________
1)
A new edition of this publication exists.
)
This publication has been withdrawn and replaced by IEC 60068-2-78.
– 8 – 60938-1 © IEC:1999
1)
IEC 60068-2-6:1995 , Environmental testing – Part 2-6: Tests – Test Fc: Vibration (sinusoidal)
IEC 60068-2-13:1983, Environmental testing – Part 2: Tests – Test M: Low air pressure
IEC 60068-2-14:1984, Environmental testing – Part 2: Tests – Test N: Change of temperature
Amendment 1 (1986)
IEC 60068-2-17:1994, Basic environmental testing procedures – Part 2: Tests – Test Q:
Sealing
IEC 60068-2-20:1979, Environmental testing – Part 2: Tests – Test T: Soldering
Amendment 2 (1987)
1)
IEC 60068-2-21:1983 , Basic environmental testing procedures – Part 2: Tests – Test U:
Robustness of terminations and integral mounting devices
Amendment 2 (1991)
Amendment 3 (1992)
1)
IEC 60068-2-27:1987 , Basic environmental testing procedures – Part 2-27: Tests – Test Ea
and guidance: Shock
IEC 60068-2-29:1987, Environmental testing – Part 2: Tests – Test Eb and guidance: Bump
1)
IEC 60068-2-30:1980 , Basic environmental testing procedures – Part 2: Tests – Test Db and
guidance: Damp heat, cyclic (12 + 12 hour cycle)
Amendment 1 (1985)
IEC 60068-2-45:1980, Environmental testing – Part 2: Tests – Test XA and guidance:
Immersion in cleaning solvents
Amendment 1 (1993)
IEC 60294:1969, Measurement of the dimensions of a cylindrical component having two axial
terminations
1)
IEC 60335-1:1991 , Safety of household and similar electrical appliances – Part 1: General
requirements
IEC 60410:1973, Sampling plans and procedures for inspection by attributes
IEC 60617 (all parts), Graphical symbols for diagrams
)
IEC 60695-2-2:1991 , Fire hazard testing – Part 2: Test methods – Section 2: Needle-flame
test
Amendment 1 (1994)
CISPR 17:1981, Methods of measurement of the suppression characteristics of passive radio
interference filters and suppression components
1)
IEC QC 001002-3:1998 , IEC Quality Assessment System for Electronic Components (IECQ) –
Rules of Procedure – Part 3: Approval procedures
ISO 1000:1992, SI units and recommendations for the use of their multiples and of certain
other units
___________
)
This publication has been withdrawn and replaced by IEC 60695-11-5.
60938-1 © IEC:1999 – 9–
2 Technical data
2.1 Units and symbols
Units, graphical symbols, letter symbols and terminology shall, whenever possible, be taken
from the following publications:
IEC 60027
IEC 60050
IEC 60617
ISO 1000
When further items are required, they shall be derived in accordance with the principles of the
documents listed above.
2.2 Definitions
For the purpose of this International Standard, the following definitions apply.
2.2.1
type
a group of components having similar design features and the similarity of whose
manufacturing techniques enables them to be grouped together either for qualification approval
or for quality conformance inspection
They are generally covered by a single detail specification.
NOTE Components described in several detail specifications, may, in some cases, be considered as belonging to
the same type.
2.2.2
style
a sub-division of a type, generally based on dimensional factors
A style may include several variants, generally of a mechanical order
2.2.3
family (of electronic components)
a group of electronic components which predominantly displays a particular physical attribute
and/or fulfils a defined function
2.2.4
sub-family (of electronic components)
a group of components within a family manufactured by similar technological methods
2.2.5
rated voltage (U )
R
rated voltage is either the maximum r.m.s. operating voltage of rated frequency or the
maximum d.c. operating voltage which may be applied continuously to the terminations of the
inductor at any temperature between the lower category temperature and the rated temperature
NOTE For inductors with only one winding, the rated voltage should only be applied between one terminal and any
conducting surface with which the case is liable to come into contact in normal use. For inductors having more than
one winding, the rated voltage may be applied across two individual windings.
2.2.6
category voltage (U )
C
maximum voltage which may be applied continuously to an inductor at its upper category
temperature
– 10 – 60938-1 © IEC:1999
2.2.7
lower category temperature
minimum external surface temperature for which the inductor has been designed to operate
continuously
2.2.8
upper category temperature
maximum external surface temperature for which the inductor has been designed to operate
continuously
NOTE The external surface temperature can be affected by internal heating due to the lead-through current. The
terminations are considered to be part of the external surface.
2.2.9
rated temperature
maximum ambient temperature at which an inductor can carry its rated current
2.2.10
rated current
maximum r.m.s. operating current at rated frequency or maximum d.c. operating current which
allows continuous operation of the inductor at the rated temperature. It is assigned by the
manufacturer for one or both of the following conditions:
a) free air (I );
RO
b) with a specified heat sink (I ).
RH
2.2.11
rated inductance (L )
R
inductance value for which the inductor has been designed and which is usually indicated upon it
2.2.12
insertion loss
ratio of the voltage before and after the insertion of the suppressor in the circuit as measured
at the terminations
NOTE 1 The insertion loss can be measured either with a symmetrical or an asymmetrical test circuit.
NOTE 2 When expressed in decibels, the insertion loss is 20 times the logarithm of the ratio stated.
2.2.13
asymmetrical test circuit
a test circuit in which the inductor under test is connected with a coaxial cable of which the
outer conductor constitutes a return path for high-frequency current
[CISPR 17:1981, 3.5 modified]
2.2.14
symmetrical test circuit
a test circuit in which the inductor under test is connected with screened conductor pairs in
which the asymmetrical voltage is small enough to be neglected
[CISPR 17:1981, 3.6 modified]
2.2.15
insulated inductor
an inductor in which all terminations connected to a section may be raised to a potential
different (but not less than the rated voltage) from that of any conducting surface with which
the case is liable to come into contact in normal use
60938-1 © IEC:1999 – 11–
2.2.16
uninsulated inductor
an inductor in which at least one of the terminations connected to a section cannot be raised to
a potential different (but not less than the rated voltage) from that of any conducting surface
with which the case is liable to come into contact in normal use
2.2.17
electromagnetic interference suppression inductor
an inductor which at mains frequency has a low impedance, but which at radio frequency has a
high inductive impedance
NOTE 1 It may be used for reducing the interference at frequencies caused by electrical equipment.
NOTE 2 These inductors are sometimes known as RF chokes.
2.2.18
current-compensated inductor
an inductor having more than one winding on a single core arranged in such a way that the
resultant magnetization caused by the current is near zero
2.2.19
earth inductor
an inductor connected in the earth lead of an equipment.
For requirements for earth inductors, see Annex C.
2.2.20
thyristor inductor
an inductor used in thyristor controlled circuits
2.2.21
mains inductor
an inductor intended for direct electrical connection to the supply mains
NOTE This inductor may form part of an equipment.
2.2.22
TV choke
an inductor designed to reduce interference mainly in the frequency range 30 MHz to 300 MHz
NOTE Unencapsulated, non-current compensated TV chokes are not within the scope of this specification, but
should be considered as part of the equipment wiring.
2.2.23
visible damage
visible damage which reduces the usability of the inductor unit for intended purpose
2.3 Preferred values
Each sectional specification shall prescribe the preferred values appropriate to the sub-family
covered by that sectional specification.
2.4 Marking
2.4.1 General
The sectional specification shall indicate the identification criteria and other information to be
shown on the inductors and the packing.
The order of priority for marking small inductors shall be specified.
– 12 – 60938-1 © IEC:1999
2.4.2 Coding
When coding is used for tolerance or date of manufacture, the method shall be selected from
those given in IEC 60062.
3 Quality assessment procedures
3.1 General
When these standards are used for the purpose of a full quality assessment system such
as the IEC quality assessment system for electronic components (IECQ), compliance to 3.4 or
3.5 is required.
When these standards are used outside quality assessment systems for purposes such as
design proving or type testing, the procedures and requirements of 3.4.1 and 3.4.3 may be
used, but the tests and parts of tests shall be applied in the order given in the test schedules.
Before inductors can be qualified according to the procedures of this clause, the manufacturer shall
obtain the approval of his organization in accordance with the provisions of IEC QC 001002-3.
For certification by an independent test laboratory the procedure of 3.4.3 shall be sufficient,
except that the test laboratory will produce the evidence of conformance.
3.2 Primary stage of manufacture
The primary stage of manufacture is the winding of the inductive element(s).
3.3 Structurally similar inductors
The grouping of structurally similar inductors for the purpose of qualification approval and
quality conformance inspection shall be prescribed in the sectional specification.
3.4 Qualification approval procedures
3.4.1 Eligibility for qualification approval
The manufacturer shall comply with 3.1.1 of IEC QC 001002-3.
3.4.2 Application for qualification approval
The manufacturer shall comply with 3.1.3 of IEC QC 001002-3.
3.4.3 Test procedure for qualification approval
In addition to the requirements of 3.4.1 and 3.4.2, the manufacturer shall produce test evidence
to show conformance to the specification requirements on the fixed sample size test schedule
given in the sectional specification.
The specimens taken to form the sample shall be selected at random from current production
or as agreed with the National supervising inspectorate (NSI).
3.4.4 Granting of qualification approval
Qualification approval shall be granted when the procedures in accordance with 3.1.4 of
IEC QC 001002-3 have been completed satisfactorily.
60938-1 © IEC:1999 – 13–
3.4.5 Maintenance of qualification approval
Qualification approval obtained as part of a quality assessment system shall be maintained by
regular demonstration of compliance with the requirements for quality conformance (see 3.5).
3.5 Quality conformance inspection
The blank detail specification(s) associated with the sectional specification shall prescribe the
test schedule for quality conformance inspection. This schedule shall also specify the grouping,
sampling and periodicity for the lot-by-lot and periodic inspection.
Operation of the switching rule for reduced inspection in group C is permitted in all sub-groups
except endurance. Sampling plans and inspection levels shall be selected from those given
in IEC 60410.
If required, more than one schedule may be specified.
3.5.1 Certified test records of released lots
When certified test records are requested by a purchaser, they shall be specified in the detail
specification.
3.5.2 Delayed delivery
Inductors held for a period exceeding three years (unless otherwise specified in the detail
specification) following the release of the lot shall, before delivery, be re-examined as specified
in the sectional specification.
Once a lot has been satisfactorily re-inspected, its quality is re-assured for three years from the
date of re-inspection.
3.5.3 Release for delivery before the completion of group B tests
When the conditions of IEC 60410 for changing to reduced inspection have been satisfied for
all group B tests, the manufacturer is permitted to release components before the completion
of such tests.
3.6 Alternative test methods
See 3.2.3.7 of IEC QC 001002-3 with the following details:
In case of dispute, for referee and reference purposes only the specified methods shall be
used.
3.7 Unchecked parameters
Only those parameters of a component which have been specified in a detail specification and
which are subject to testing can be assumed to be within the specified limits.
It cannot be assumed that any unspecified parameter will remain unchanged from one
component to another. Should it be necessary, for any reason, for further parameters to be
controlled, then a new, more extensive specification should be used.
The additional test methods shall be fully described and appropriate limits, sampling plans and
inspection levels specified.
– 14 – 60938-1 © IEC:1999
4 Test and measurement procedure
4.1 General
The sectional and/or blank detail specification shall contain the tests to be made, which
measurements are to be made before and after each test or sub-group of tests and the
sequence in which they shall be carried out. The stages of each test shall be carried out in the
order written. The measuring conditions shall be the same for initial and final measurements.
If national specifications within any quality assessment system include methods other than
those specified in the above standards, they shall be fully described.
Limits given in all specifications are absolute limits. The principle to take measurement
uncertainty into account shall be applied (see IEC QC 001002-3, Annex C).
4.2 Standard atmospheric conditions
4.2.1 Standard atmospheric conditions for testing
Unless otherwise specified, all tests and measurements shall be made under standard
atmospheric conditions for testing as given in 5.3 of IEC 60068-1:
– temperature: 15 °C to 35 °C;
– relative humidity: 25 % to 75 %;
– air pressure: 86 kPa to 106 kPa.
Before the measurements are made, the component shall be stored at the measuring
temperature for a time sufficient to allow the entire component to reach this temperature. The
period as prescribed for recovery at the end of a test is normally sufficient for this purpose.
When measurements are made at a temperature other than the specified temperature, the results
shall, where necessary, be corrected to the specified temperature. The ambient temperature
during the measurements shall be stated in the test report. In the event of a dispute, the
measurements shall be repeated, using one of the referee temperatures (as given in 4.2.3) and
such other conditions as are prescribed in this specification.
When tests are conducted in a sequence, the final measurements of one test may be taken as
the initial measurements for the succeeding test.
During measurements, the component shall not be exposed to draughts, direct sunlight or
other influences likely to cause errors.
4.2.2 Recovery conditions
Unless otherwise specified, recovery shall take place under the standard atmospheric
conditions for testing (4.2.1).
If recovery under closely controlled conditions is necessary, the controlled recovery conditions
of 5.4.1 of IEC 60068-1 shall be used.
Unless otherwise specified in the relevant specification, a duration of 1 h to 2 h shall be used.
4.2.3 Referee conditions
For referee purposes, one of the standard atmospheric conditions for referee tests taken
from 5.2 of IEC 60068-1, as given in Table 1, shall be selected:
60938-1 © IEC:1999 – 15–
Table 1 – Reference test: standard atmospheric conditions
Temperature Relative Air pressure
humidity
°C kPa
%
63 to 67 86 to 106
20 ± 1
48 to 52 86 to 106
23 ± 1
48 to 52 86 to 106
25 ± 1
63 to 67 86 to 106
27 ± 1
4.2.4 Reference conditions
For reference purposes, the standard atmospheric conditions for reference given in 5.1 of
IEC 60068-1 apply:
– temperature: 20 °C;
– air pressure: 101,3 kPa.
4.3 Drying
Unless otherwise specified in the relevant specification, the inductor shall be conditioned for
96 h ± 4 h by heating in a circulating air oven at a temperature of 55 °C ± 2 °C and a relative
humidity not exceeding 20 %.
The inductor shall then be allowed to cool in a desiccator using a suitable desiccant, such as
activated alumina or silica gel, and shall be kept therein from the time of removal from the oven
to the beginning of the specified tests.
4.4 Visual examination and check of dimensions
4.4.1 Visual examination
The condition, workmanship and finish shall be satisfactory as checked by visual examination
(see 2.2.23).
Marking shall be legible, as checked by visual examination and shall conform to the
requirements of the detail specification.
4.4.2 Dimensions (gauging)
The dimensions indicated in the detail specification as being suitable for gauging shall be
checked, and shall comply with the values prescribed in the detail specification.
When applicable, measurements shall be made in accordance with IEC 60294.
4.4.3 Dimensions (detail)
All dimensions prescribed in the detail specification shall be checked and shall comply with the
values prescribed.
4.4.4 Creepage distances and clearances
For main inductors, creepage distances and clearances on the outside of the inductor between
live parts of different polarity or between live parts and a metal case shall be not less than the
appropriate values given in Table 2.
– 16 – 60938-1 © IEC:1999
Table 2 – Creepage distances and clearances
Rated voltage
U ≤ 130 V 130 V < U ≤ 250 V 250 V < U ≤ 500 V 500 V < U ≤ 760 V
R R R R
Point of
measurement
Creepage Clearance Creepage Clearance Creepage Clearance Creepage Clearance
distance distance distance distance
mm mm mm mm mm mm mm mm
Between live 2,0 1,5 3,0 2,5 4,0 3,0 6,3 5,5
parts of different
polarity
Between live 2,0 1,5 4,0 3,0 6,3 5,5 6,3 5,5
parts and other
metal parts over
basic insulation
Between live 8,0 8,0 8,0 8,0
parts and other
metal parts over
reinforced
insulation
NOTE The values are for basic insulation in accordance with Clause 29 of IEC 60335-1.
Compliance shall be checked by measurement according to the rules laid down in IEC 60335-1
for measurement on the outside of the inductor. Additional requirements may be necessary, for
example for drip-proof or splash-proof inductors.
4.5 Insulation resistance
4.5.1 Unless otherwise specified in the relevant specification, the insulation resistance shall
be measured, at the d.c. voltage specified in Table 3.
Table 3 – Measuring voltage
Voltage rating of inductor Measuring voltage
V V
U or U < 10 U or U ± 10 %
R C C R
10 ≤ U or U < 100 10 ± 1 *
R C
100 ≤ U or U < 500 100 ± 15
R C
500 ≤ U or U 500 ± 50
R C
* When it can be demonstrated that the voltage has no influence on
the measuring result, or that a known relationship exists, measure-
ment can be performed at voltages up to the rated or category
voltage (10 V shall be used in case of dispute).
U is the rated voltage for use in defining the measuring voltage to be used under standard
R
atmospheric conditions for testing.
U is the category voltage for use in defining the measuring voltage to be used at the upper
C
category temperature.
60938-1 © IEC:1999 – 17–
4.5.2 The insulation resistance shall be measured between the measuring points defined in
Table 4, specified in the relevant specification.
Test A, between terminations, applies to all inductors, whether insulated or not.
Test B, internal insulation, applies to insulated inductors in uninsulated metal cases.
Test C, external insulation, applies to insulated inductors in non-metallic cases or in insulated
metal cases. For this test, the measuring voltage shall be applied using one of the three
following methods as specified in the relevant specification.
4.5.2.1 Foil method
A metal foil shall be closely wrapped around the body of the inductor. For inductors with axial
terminations this foil shall extend beyond each end by not less than 5 mm, provided that a
minimum distance of 1 mm can be maintained between the foil and the terminations. If this
minimum distance cannot be maintained, the extension of the foil shall be reduced by as much
as is necessary to establish the distance of 1 mm.
For inductors with unidirectional terminations, a minimum distance of 1 mm shall be maintained
between the edge of the foil and each termination.
4.5.2.2 Method for inductors with mounting devices
The inductor shall be mounted in its normal manner on a metal plate, which extends at least
13 mm in all direct
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