Fixed inductors for electromagnetic interference suppression - Part 1: Generic specification

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. It may not necessarily apply in its entirety to inductors intended for use on motor vehicles, in aircraft or for marine applications. This consolidated version consists of the second edition (1999) and its amendment 1 (2006). Therefore, no need to order amendment in addition to this publication.

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Publication Date
27-Nov-2006
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16-Jun-2021
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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
IEC 60938-1:1999+A1:2006(E)
---------------------- Page: 1 ----------------------
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

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thus ensuring that the content reflects current technology. Information relating to

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publications (see below) in addition to new editions, amendments and corrigenda.
Information on the subjects under consideration and work in progress undertaken

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---------------------- Page: 2 ----------------------
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
Commission Electrotechnique Internationale
International Electrotechnical Commission
МеждународнаяЭлектротехническаяКомиссия
For price, see current catalogue
---------------------- Page: 3 ----------------------
– 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

---------------------- Page: 4 ----------------------
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

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– 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).
---------------------- Page: 6 ----------------------
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.
---------------------- Page: 7 ----------------------
– 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

---------------------- Page: 8 ----------------------
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
---------------------- Page: 9 ----------------------
– 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 )

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.
---------------------- Page: 10 ----------------------
60938-1 © IEC:1999+A1:2006(E) – 9 –
2.2.6
category voltage (U )

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 );
b) with a specified heat sink (I ).
2.2.11
rated inductance (L )

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]
---------------------- Page: 11 ----------------------
– 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

---------------------- Page: 12 ----------------------
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.
---------------------- Page: 13 ----------------------
– 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
...

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