IEC 60938-1:2021
(Main)Fixed inductors for electromagnetic interference suppression - Part 1: Generic specification
Fixed inductors for electromagnetic interference suppression - Part 1: Generic specification
IEC 60938-1:2021 applies to inductors designed for electromagnetic interference suppression intended for use within all kind of electric and electronic equipment.
In this generic specification, normative references and terms and definitions are given. It also prescribes general requirements and the suitable test and measurement procedures for interference suppression inductors. Annex B states special requirements for earth inductors.
This edition includes the following significant technical changes with respect to the previous edition:
a) material tests added;
b) improved readability and clear separation between test descriptions in the generic spec and requirements in the sectional specification;
c) creepage and clearance requirements are now defined in sectional specifications only;
d) AC testing for voltage test included.
Inductances fixes d’antiparasitage - Partie 1: Spécification générique
L’IEC 60938-1:2021 s'applique à des inductances conçues pour l’antiparasitage et destinées à être utilisées dans tous les types d’équipements électriques et électroniques.
La présente spécification générique comporte des références normatives ainsi que des termes et définitions. Elle spécifie également les exigences générales et les modes opératoires d’essai et de mesure appropriés pour les inductances d’antiparasitage. L’Annexe B précise les exigences particulières applicables aux inductances de terre.
Cette édition inclut les modifications techniques majeures suivantes par rapport à l'édition précédente:
a) ajout d’essais de matériaux;
b) amélioration de la lisibilité et séparation claire entre les descriptions des essais dans la spécification générique et les exigences dans la spécification intermédiaire;
c) les exigences de ligne de fuite et de distance d’isolement sont désormais définies uniquement dans les spécifications intermédiaires;
d) Les essais de tension en courant alternatif sont inclus.
General Information
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Standards Content (Sample)
IEC 60938-1 ®
Edition 3.0 2021-06
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
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 3.0 2021-06
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Fixed inductors for electromagnetic interference suppression –
Part 1: Generic specification
Inductances fixes d’antiparasitage –
Partie 1: Spécification générique
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 29.100.10; 31.020 ISBN 978-2-8322-9883-1
– 2 – IEC 60938-1:2021 © IEC 2021
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 8
2 Normative references . 8
3 Terms, definitions and conventions . 9
3.1 Terms and definitions . 9
3.2 Conventions . 11
4 General requirements . 11
4.1 General . 11
4.2 Preferred values . 12
4.2.1 General . 12
4.2.2 Rated current . 12
4.2.3 Temperature de-rated current . 12
4.3 Information to be given in a detail specification . 12
4.3.1 General . 12
4.3.2 Outline drawing and dimensions . 12
4.3.3 Mounting . 13
4.3.4 Ratings and characteristics . 13
4.4 Insulated inductors . 13
4.5 Marking . 13
5 Tests and measurement procedures . 14
5.1 General . 14
5.2 Standard atmospheric conditions . 14
5.3 Visual examination . 14
5.4 Insulation resistance . 14
5.5 Voltage test . 15
5.6 Inductance . 16
5.7 Resistance . 16
5.8 Insertion loss . 16
5.9 Temperature rise . 16
5.10 Impulse voltage. 16
5.11 Endurance . 17
5.12 Robustness of terminations . 17
5.13 Vibration . 17
5.14 Shock . 17
5.15 Resistance to soldering heat . 18
5.16 Solderability . 20
5.16.1 General . 20
5.16.2 Preconditioning . 20
5.16.3 Test procedure . 21
5.16.4 Final inspection, measurements, and requirements. 21
5.17 Rapid change of temperature . 21
5.18 Container sealing . 21
5.19 Climatic sequence. 21
5.19.1 General . 21
5.19.2 Dry heat . 21
5.19.3 Damp heat, cyclic, test Db, first cycle . 22
5.19.4 Cold. 22
5.19.5 Low air pressure . 22
5.19.6 Damp heat, cyclic, test Db, remaining cycles . 22
5.20 Damp heat, steady state . 23
5.21 Passive flammability . 23
5.22 Glow wire . 23
5.23 Ball pressure. 23
5.24 Component solvent resistance . 23
5.25 Solvent resistance of marking . 24
Annex A (normative) Measuring points for electrical tests and measurements . 25
A.1 General . 25
A.2 Foil method . 25
A.3 Method for inductors with mounting devices . 25
A.4 V-block method . 26
Annex B (normative) Requirements for earth inductors . 27
Annex C (normative) Example of a suitable circuit for the voltage endurance test . 28
Annex X (informative) Cross-references to the previous edition of this document . 29
Bibliography . 31
Figure 1 – Relevant specification . 7
Figure 2 – Relation between ambient temperature and applied current . 12
Figure 3 – Temperature profile for reflow simulation. 19
Figure A.1 – Examples how to connect electrical tests . 26
Figure C.1 – Test circuit for endurance voltage . 28
Table 1 – Standard atmospheric conditions . 14
Table 2 – Measuring voltage for insulation resistance testing . 15
Table 3 – Temperatures for reflow simulation with different solder paste alloy types . 20
Table 4 – Number of remaining cycles for damp heat . 22
Table A.1 – Measuring points for electrical tests . 25
Table B.1 – Minimum copper cross-sectional area of earth inductor’s winding . 27
– 4 – IEC 60938-1:2021 © IEC 2021
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 itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
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.
IEC 60938-1 has been prepared by IEC technical committee 40: Capacitors and resistors for
electronic equipment. It is an International Standard.
This third edition cancels and replaces the second edition published in 1999. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) material tests added;
b) improved readability and clear separation between test descriptions in the generic spec and
requirements in the sectional specification;
c) creepage and clearance requirements are now defined in sectional specifications only;
d) AC testing for voltage test included.
The text of this International Standard is based on the following documents:
FDIS Report on voting
40/2834/FDIS 40/2851/RVD
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this International Standard is English.
A list of all parts in the IEC 60938 series, published under the general title Fixed inductors for
electromagnetic interference suppression, can be found on the IEC website.
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/standardsdev/publications.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under webstore.iec.ch in the data related to the
specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
– 6 – IEC 60938-1:2021 © IEC 2021
INTRODUCTION
The specification system for fixed inductors for electromagnetic interference suppression is
structured in a hierarchical system consisting of the following specification types.
Generic specification
The generic specification covers all subjects mainly common to the family of fixed inductors for
electromagnetic interference suppression, such as terminology, methods of measurement and
tests. Where the individual subjects require the prescription conditions or parameters specific
to the particular sub-family or type of inductor, such prescriptions are required to be given by
one of the subordinate specifications.
For the scope of fixed inductors, the numeric reference to the generic specification is
IEC 60938-1.
Sectional specification
Sectional specifications cover all subjects additional to those given in the generic specification,
which are specific to a defined sub-group of fixed inductors for electromagnetic interference
suppression. These subjects normally are preferred values for dimensions and characteristics,
relevant prescriptions for test methods given in the generic specification, prescriptions for
sampling and for the preparation of specimen, recommended test severities and preferred
acceptance criteria. The sectional specification also outlines the structure and scope of the test
schedules, which are to be applied in all subordinate detail specifications.
For the scope of fixed inductors for electromagnetic interference suppression, the numeric
reference to the only sectional specification is 60938-2 for line chokes.
Detail specification
Detail specifications give directly, or by making reference to other specifications, all information
necessary to completely describe a given type and range of fixed inductors for electromagnetic
interference suppression, including prescriptions of all values for dimensions and
characteristics. They also give all information required for all applied test severities and
acceptance criteria, and the completed test schedules.
Detail specifications can be either specifications within the IEC system, another specification
system linked to IEC, or specified by the manufacturer or user.
Blank detail specification
The hierarchical system of specifications can be supplemented by one or more blank detail
specifications to a sectional specification, which are used to ensure a uniform presentation of
detail specifications. The blank detail specifications provide the specification writer with a
template on the layout to be adopted and on the information to be given and with guidance for
the preparation of detail specifications in line with the requirements of the superior generic or
sectional specifications. Blank detail specifications are not considered to be relevant
specifications since they do not themselves describe any particular component.
The presence of an established hierarchical specification system with blank detail specifications
permits the preparation of detail specifications, even outside of the relevant IEC technical
committee.
For the scope of fixed inductors for electromagnetic interference suppression, the numeric
references to blank detail specifications are, for example, IEC 60938-2-1, if related to the
sectional specification IEC 60938-2.
Relevant specification
In this system, the term "relevant specification" addresses subordinate specifications containing
specific requirements, where applicable (see Figure 1).
Any generic or sectional specification can use abstract and universal references to subordinate
specifications of either hierarchical level by use of the expression "relevant specification".
Key
1) Indicates the range of "relevant specifications" to the superior generic specification, where applicable.
2) Indicates the range of "relevant specifications" to the superior sectional specification, where applicable.
Figure 1 – Relevant specification
– 8 – IEC 60938-1:2021 © IEC 2021
FIXED INDUCTORS FOR ELECTROMAGNETIC
INTERFERENCE SUPPRESSION –
Part 1: Generic specification
1 Scope
This part of IEC 60938 applies to inductors designed for electromagnetic interference
suppression intended for use within all kind of electric and electronic equipment.
In this generic specification, normative references and terms and definitions are given. It also
prescribes general requirements and the suitable test and measurement procedures for
interference suppression inductors. Annex B states special requirements for earth inductors.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements 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.
CISPR 17, Methods of measurement of the suppression characteristics of passive EMC filtering
devices
IEC 60027 (all parts), Letter symbols to be used in electrical technology
IEC 60050 (all parts), International Electrotechnical Vocabulary (IEV) (available at
www.electropedia.org)
IEC 60060-1, High-voltage test techniques – Part 1: General definitions and test requirements
IEC 60062, Marking codes for resistors and capacitors
IEC 60068-1, Environmental testing – Part 1: General and guidance
IEC 60068-2-1, Environmental testing – Part 2-1: Tests – Tests A: Cold
IEC 60068-2-2, Environmental testing – Part 2-2: Tests – Tests B: Dry Heat
IEC 60068-2-6, Environmental testing – Part 2-6: Tests – Test Fc: Vibration (sinusoidal)
IEC 60068-2-13, Environmental testing – Part 2-13: Tests – Test M: Low air pressure
IEC 60068-2-14, Environmental testing – Part 2-14: Tests – Test N: Change of temperature
IEC 60068-2-17, Basic environmental testing procedures – Part 2-17: Tests – Test Q: Sealing
IEC 60068-2-20, Environmental testing – Part 2-20: Tests – Test T: Test methods for
solderability and resistance to soldering heat of devices with leads
IEC 60068-2-21, Environmental testing – Part 2-21: Tests – Test U: Robustness of terminations
and integral mounting devices
IEC 60068-2-27, Environmental testing – Part 2-27: Tests – Test Ea and guidance: Shock
IEC 60068-2-30, Environmental testing – Part 2-30: Tests – Test Db: Damp heat, cyclic
IEC 60068-2-45, Basic environmental testing procedures – Part 2-45: Tests – Test XA and
guidance: Immersion in cleaning solvents
IEC 60068-2-58, Environmental testing – Part 2-58: Tests – Test Td: Test methods for
solderability, resistance to dissolution of metallization and to soldering heat of surface mounting
devices (SMD).
IEC 60068-2-78, Environmental testing – Part 2-78: Tests – Test Cab: Damp heat, steady state
IEC 60335-1, Household and similar electrical appliances – Part 1: General requirements
IEC 60617, Graphical symbols for diagrams (available at http://std.iec.ch/iec60617)
IEC 60695-2-11, Fire hazard testing – Part 2-11: Glowing/hot-wire based test methods – Glow-
wire flammability test method for end-products (GWEPT)
IEC 60695-2-12, Fire hazard testing – Part 2-12: Glowing/hot-wire based test methods – Glow-
wire flammability index (GWFI) test method for materials
IEC 60695-2-13, Fire hazard testing – Part 2-13: Glowing/hot-wire based test methods – Glow-
wire ignition temperature (GWIT) test method for materials
IEC 60695-10-2, Fire hazard testing – Part 10-2: Abnormal heat – Ball pressure test method
IEC 60695-11-10, Fire hazard testing – Part 11-10: Test flames – 50 W horizontal and vertical
flame test methods
IEC 60695-11-20, Fire hazard testing – Part 11-20: Test flames – 500 W flame test method
ISO 80000-6, Quantities and units – Part 6: Electromagnetism
3 Terms, definitions and conventions
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
For the purposes of this document, the following terms and definitions apply.
3.1 Terms and definitions
3.1.1
choke
inductor
construction that employs one or more windings for a frequency-dependent impedance
– 10 – IEC 60938-1:2021 © IEC 2021
3.1.2
rated voltage
U
R
maximum RMS operating voltage of the rated frequency or the maximum DC operating voltage
that can be applied continuously to the terminations of the inductor
Note 1 to entry: Because the rated voltage against any surrounding conducting surface is defined by the mounting
in the application, an inductor with only one winding can have no rated voltage.
3.1.3
lower category temperature
minimum surface temperature for which the inductor has been designed to operate continuously
3.1.4
upper category temperature
T
c
maximum surface temperature for which the inductor has been designed to operate
continuously
3.1.5
rated temperature
T
r
maximum ambient temperature at which an inductor can carry its rated current
3.1.6
rated current
I
r
maximum RMS operating current at rated frequency or maximum DC operating current, which
allows continuous operation of the inductor at the rated temperature
3.1.7
nominal inductance
L
n
inductance value for which the inductor has been designed and which is usually indicated upon
it
3.1.8
insertion loss
ratio of a voltage before and after the insertion of the suppressor in the circuit as measured in
accordance with CISPR 17
3.1.9
insulated inductor
inductor in which all live parts, except for the terminations, are protected against touch or
contact with surrounding conductive parts
3.1.10
uninsulated inductor
inductor in which at least one live metal part, other than a termination, is not protected against
touch or contact with surrounding conductive parts
3.1.11
common-mode inductor
current-compensated choke
inductor having more than one winding on a single core arranged in such a way that the resultant
magnetization caused by the symmetrical current is near zero
3.1.12
earth inductor
inductor connected in series with the protective conductor of equipment
3.1.13
power line choke
mains inductor
inductor intended for direct electrical connection to the supply mains
3.1.14
clearance
shortest distance in air between two conductive parts or between a conductive part and a
touchable surface
3.1.15
creepage
shortest distance between two conductive parts or between a conductive part and a touchable
surface, measured over the surface of the insulator
3.1.16
micro-environment
conditions that immediately surround the clearance or creepage distance under consideration
3.1.17
pollution degree
level of pollution present at the location on or in a product where the clearance and creepage
measurement is made
3.2 Conventions
In IEC standards, a "rated" value, e.g. a rated temperature, is a value under which a component
may be operated continuously. It is a maximum limit, which may not be exceeded.
A "nominal" value is a value a component typically has, e.g. a nominal inductance. A nominal
value has an upper and a lower tolerance limit and within this range the respective characteristic
can be measured.
4 General requirements
4.1 General
If possible, units, graphical symbols, letter symbols and terminology shall be taken from the
following publications:
– IEC 60027,
– IEC 60050,
– IEC 60617,
– ISO 80000-6.
When further items are required, they shall be derived in accordance with the principles of the
documents listed above.
– 12 – IEC 60938-1:2021 © IEC 2021
4.2 Preferred values
4.2.1 General
In general, there are no preferred values for nominal inductance, rated voltage, rated current
or rated frequency, because different applications require many different designs. Sectional
specifications may define preferred values.
Inductors designed for electromagnetic interference suppression attenuate common-mode and
differential-mode currents differently. They can be named common-mode inductor or
differential-mode inductor depending on the primary use for which they are designed.
4.2.2 Rated current
For every inductor, the rated current I shall be assigned by the manufacturer for one or both of
r
the following conditions:
a) free air (I );
RO
b) with a specified heat sink (I ).
RH
4.2.3 Temperature de-rated current
Figure 2 shows the relation between applied current and ambient temperature.
Figure 2 – Relation between ambient temperature and applied current
If not stated otherwise in the detail specification, a linear de-rating of applied current over
ambient temperature is assumed up to zero current at the upper category temperature.
4.3 Information to be given in a detail specification
4.3.1 General
Detail specifications shall be derived from the relevant blank detail specification.
Detail specifications shall not specify requirements inferior to those of the generic or sectional
specification. When more severe requirements are included, they shall be listed separately.
4.3.2 Outline drawing and dimensions
There shall be an illustration of the inductor as an aid to easy recognition and for comparison
of the inductor with others. Dimensions and their associated tolerances, which affect
interchangeability and mounting, shall be indicated on the drawing. All dimensions shall be
stated in millimetres.
The numerical values shall be given for the length of the body, the width and height of the body
or for cylindrical types, the body diameter, and the length and diameter of the terminations.
When necessary, for example when a number of items (inductance values/ voltage ranges) are
covered by a detail specification, the dimensions and their associated tolerances shall be
placed in a table below the drawing.
When the configuration is other than that described above, the detail specification shall state
such dimensional information to describe the inductor adequately. When the inductor is not
designed for use on printed boards, this shall be clearly stated in the detail specification.
4.3.3 Mounting
The detail specification shall specify the method of mounting to be recommended for normal
use and the method that is mandatory for the application of the vibration and shock tests. The
design of the inductor can be such that special mounting fixtures are required in its use. In this
case, the detail specification shall describe the mounting fixtures and they shall be used in the
application of shock and vibration tests. The specified heat sink shall be used in the application
of the endurance test.
4.3.4 Ratings and characteristics
The ratings and characteristics shall be in accordance with the relevant clauses of this
specification. Additional characteristics may be listed when they are considered necessary to
specify adequately the inductor for design and application purposes.
4.4 Insulated inductors
Insulated inductors may be built either with a housing, or with isolated wires whose isolation
provides basic insulation, e.g. TIW, FIW-wires, PVC-isolated wires, wires in insulation sleeves
or the like. The isolated wires or the insulating materials used shall be in accordance with
relevant IEC standards.
Instead of fulfilling requirements for clearance and creepage inside inductors, the windings may
be insulated by potting or insulation sleeves or the windings may be built from wires with basic
insulation like TIW, FIW, PVC-isolated wires or the like.
Insulation materials used between terminals and windings, for housing or potting shall be
certified to a minimum rating of V-2, VTM-2 or HF-2 in accordance with IEC 60695-11-10 and
IEC 60695‑11‑20 (or UL 94) at the appropriate minimum thickness, which is determined by the
smallest thickness of insulation in direct contact with a conductor.
4.5 Marking
Necessary marking in accordance with the relevant specifications shall be prescribed in the
detail specification. Deviations from these requirements shall be listed separately and the
reason for them shall be stated specifically in the detail specification.
The sectional specification shall indicate the identification criteria and other information to be
shown on the inductors and its packaging. The order of priority for marking small components
shall be specified. When coding is used for inductance values, tolerance or date of manufacture,
the method shall be selected from those given in IEC 60062.
– 14 – IEC 60938-1:2021 © IEC 2021
5 Tests and measurement procedures
5.1 General
The relevant 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.
5.2 Standard atmospheric conditions
Unless otherwise specified, all tests and measurements shall be made under standard
atmospheric conditions for testing as given in Table 1:
Table 1 – Standard atmospheric conditions
Temperature 15 °C to 35 °C;
Relative humidity: 25 % to 75 %;
Air pressure: 86 kPa to 106 kPa;
Before measurements are made, components shall be stored at the measuring temperature for
a period sufficient to allow the entire component to reach this temperature. The period stated
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 be corrected to the specified temperature. The ambient temperature during the
measurements shall be stated in the test report. 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.
Recovery shall also take place under the standard atmospheric conditions, unless otherwise
specified in the relevant specification. For reference conditions, referee conditions or recovery
under closely controlled conditions, refer to IEC 60068-1.
5.3 Visual examination
The condition, workmanship and finish shall be satisfactory as checked by visual examination.
Marking shall be legible, as checked by visual examination, and shall conform to the
requirements of the detail specification.
The dimensions indicated in the detail specification shall be checked.
5.4 Insulation resistance
Unless otherwise specified in the relevant specification, the insulation resistance shall be
measured, at the DC voltage specified in Table 2.
Table 2 – Measuring voltage for insulation resistance testing
Voltage rating of inductor Measuring voltage
V V
U < 10 V U ± 10 %
R R
10 ≤ U < 100 V 10 ± 1
R
100 ≤ U < 500 V 100 ± 15
R
500 ≤ U < 1 000 V 500 ± 50
R
1 000 ≤ U < 1 500 V 1 000 ± 100
R
The insulation resistance shall be measured after the voltage has been applied for 60 s ± 5 s,
unless otherwise prescribed in the detail specification. The temperature at which the
measurement is made shall be noted. If this temperature differs from 20 °C, a correction may
be made by multiplying by the appropriate correction factor.
The insulation resistance shall be measured between the measuring points defined in
Table A.1.
The detail specification shall prescribe:
a) tests and measuring voltage for each test;
b) for test C, the method of applying the voltage;
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.
5.5 Voltage test
The safety and the quality of the insulation of inductors in accordance with this document are
tested by the voltage test. The voltage test is not only to be performed as a type approval test,
but also as a routine test on every component manufactured. While the type approval voltage
test (with a duration of e.g. 1 min) can be a destructive test, the routine test should not exceed
2 s to stay non-destructive. However, repeated voltage proof testing can damage the
components and should be avoided.
Type approval voltage tests for AC inductors shall be made with AC voltage. DC inductors shall
be tested with DC voltage. For routine testing, AC or DC tests are supposed to be safe
regardless whether AC or DC inductors are tested.
The detail specification shall prescribe:
a) test voltages;
b) for test C, the method of applying the voltage;
c) the time for which the voltage is applied;
d) any other requirement.
The specified test voltage is applied instantaneously via the internal resistance of the power
supply for the time specified in the detail specification. For each of the specified tests, there
shall be no sign of breakdown or flashover during the test period.
– 16 – IEC 60938-1:2021 © IEC 2021
5.6 Inductance
The inductance shall be measured using an appropriate impedance measurement device.
According to Annex A, inductance is measured between 1 and 3 or 2 and 4. As the measured
value of the inductance can be a function of current, frequency and temperature, these
parameters shall be recorded in the test report and shall remain constant throughout the test.
The measuring current or voltage and frequency shall be specified in the detail specification.
The measured inductance shall be within the tolerance declared in the detail specification.
5.7 Resistance
Using a DC measuring method with an applied voltage of less than 10 V, the resistance between
any input terminal and the corresponding output terminal shall be measured and shall not
exceed the limit stated in the detail specification.
5.8 Insertion loss
The measurement method shall be selected from those described in CISPR 17. Insertion loss
is determined for common mode with an asymmetrical circuit and differential mode with a
symmetrical circuit. Normal mode with an unsymmetrical circuit is optional. Requirements shall
be given in the sectional specification.
5.9 Temperature rise
Prior to the test, the measurements stated in the detail specification shall be made.
This test leads to an internal temperature rise of the inductor under rated conditions. This
internal temperature rise indicates whether the thermal conditions valid for the insulation
materials used for the inductor are met.
The inductors shall be submitted to a temperature rise test. The inductors shall be placed in the
test chamber in such a manner that no extra heating due to close spacing of the inductors
occurs. In case of doubt, a spacing of 25 mm shall be used.
The inductors shall be mounted in the manner specified by the manufacturer. When the
manufacturer specifies a rated current for both free air and heat sink conditions, the test shall
be carried out in the free air condition.
The specimens shall be introduced into a test chamber with a temperature equal to the ra
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