IEC 60938-2:2021

Fixed inductors for electromagnetic interference suppression - Part 2: Sectional specification on power line chokes

IEC 60938-2:2021 applies to fixed inductors designed for electromagnetic interference suppression, which will be connected to an AC mains or other supply with a nominal voltage not exceeding 1 000 V AC RMS or 1 500 V DC with a nominal frequency not exceeding 400 Hz.
This sectional specification is restricted to fixed inductors for which safety tests are appropriate. This implies that inductors specified according to this specification will either be connected to mains supplies, when compliance with the mandatory tests of Annex A is necessary, or used in other circuit positions where the equipment specification prescribes that some or all of these safety tests are required.
The object of this document is to prescribe standard requirements for safety tests, preferred ratings and characteristics, to select from IEC 60938-1 the appropriate methods of test and to give general performance requirements for suppression inductors.
This edition includes the following significant technical changes with respect to the previous edition:
- the test plan for performance testing has been removed; mandatory safety tests and optional performance tests are listed in one test plan in Annex B;
- requirements for Thyristor-Chokes have been withdrawn;
- material requirements are harmonized with IEC 60939-3 and UL 60939-3;
- AC chokes up to 1 000 V and DC chokes up to 1 500 V are now in the Scope.

Inductances fixes d'antiparasitage - Partie 2: Spécification intermédiaire sur les bobines d’arrêt pour ligne électrique

L'IEC 60938-2:2021 s'applique à des inductances fixes conçues pour s’opposer aux perturbations électromagnétiques, qui sont connectées à un réseau d’alimentation à courant alternatif ou à une autre source d’alimentation dont la tension nominale ne dépasse pas 1 000 V (valeur eff.) en courant alternatif ou 1 500 V en courant continu avec une fréquence nominale qui ne dépasse pas 400 Hz.
La présente spécification intermédiaire se limite à des inductances fixes pour lesquelles des essais de sécurité sont souhaitables. Cela signifie que les inductances décrites conformément à la présente spécification sont, soit reliées à l'alimentation secteur, lorsque la conformité aux essais obligatoires de l’Annexe A est nécessaire, soit utilisées en d'autres positions du circuit pour lesquelles la spécification applicable à l'équipement indique que certains ou l'ensemble de ces essais de sécurité sont exigés.
Le présent document a pour objet de prescrire des exigences normalisées d'essais de sécurité ainsi que des valeurs assignées et caractéristiques préférentielles, qui permettent de choisir à partir de l’IEC 60938-1 les méthodes d'essai appropriées et de fournir des exigences générales de performance applicables aux inductances d'antiparasitage.
Cette édition inclut les modifications techniques majeures suivantes par rapport à l'édition précédente.
- le programme d’essai pour les essais de performance a été supprimé; les essais de sécurité obligatoires et les essais de performance facultatifs sont énumérés dans un seul programme d’essai à l’Annexe B;
- les exigences relatives aux bobines d’arrêt à thyristor ont été supprimées;
- les exigences relatives aux matériaux sont alignées sur les normes IEC 60939-3 et UL 60939-3;
- les bobines d’arrêt à courant alternatif d’une tension jusqu’à 1 000 V et les bobines d’arrêt à courant continu d’une tension jusqu’à 1 500 V sont désormais incluses dans le Domaine d’application.

General Information

• Status: Published
• Publication Date: 19-Jul-2021
• ICS: 29.100.10 - Magnetic components
• ICS: 31.020 - Electronic components in general
• Technical Committee: TC 40 - Capacitors and resistors for electronic equipment
• Drafting Committee: MT 60938-2 - TC 40/MT 60938-2
• Current Stage: PPUB - Publication issued
• Start Date: 13-Aug-2021
• Completion Date: 20-Jul-2021

Relations

• Revises: IEC 60938-2:1999/AMD1:2006 - Amendment 1 - Fixed inductors for electromagnetic interference suppression - Part 2: Sectional specification
• Effective Date: 05-Sep-2023
• Revises: IEC 60938-2:1999 - Fixed inductors for electromagnetic interference suppression - Part 2: Sectional specification
• Effective Date: 05-Sep-2023

Standards Content (Sample)

IEC 60938-2 ®
Edition 3.0 2021-07
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Fixed inductors for electromagnetic interference suppression –
Part 2: Sectional specification on power line chokes

Inductances fixes d’antiparasitage –
Partie 2: Spécification intermédiaire sur les bobines d’arrêt pour ligne électrique

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IEC 60938-2 ®
Edition 3.0 2021-07
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Fixed inductors for electromagnetic interference suppression –

Part 2: Sectional specification on power line chokes

Inductances fixes d’antiparasitage –

Partie 2: Spécification intermédiaire sur les bobines d’arrêt pour ligne électrique

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 29.100.10; 31.020 ISBN 978-2-8322-1002-2

– 2 – IEC 60938-2:2021 © IEC 2021
CONTENTS
FOREWORD . 5
1 Scope . 7
2 Normative references . 7
3 Terms and definitions . 8
4 General requirements . 9
4.1 General . 9
4.2 Preferred values of ratings and characteristics . 9
4.2.1 Climatic categories . 9
4.2.2 Nominal inductance and tolerance . 9
4.2.3 Rated voltage U . 9
R
4.2.4 Rated temperature T . 9
r
4.2.5 Rated current I . 10
r
4.3 Information to be given in a detail specification . 10
4.3.1 General . 10
4.3.2 Outline drawing and dimensions . 10
4.3.3 Mounting . 11
4.3.4 Ratings and characteristics . 11
4.4 Insulated inductors for power line applications . 11
4.5 Marking . 11
5 Safety tests for approval . 12
5.1 General . 12
5.1.1 Approval on the basis of the fixed sample size procedures . 12
5.1.2 Structurally similar inductors . 12
5.1.3 Sampling . 13
5.2 Standard atmospheric conditions . 13
5.3 Visual examination . 13
5.3.1 Dimensions (gauging) . 13
5.3.2 Dimensions (detail) . 13
5.4 Insulation resistance . 14
5.5 Voltage test . 14
5.6 Inductance . 15
5.7 Line resistance . 15
5.8 Insertion loss (optional) . 15
5.9 Temperature rise (applies to inductors with a mass > 5 g only) . 15
5.9.1 General . 15
5.9.2 Test method . 15
5.9.3 Requirements . 16
5.10 Impulse voltage (applies to inductors with more than one winding only) . 16
5.10.1 Test conditions . 16
5.10.2 Initial measurements . 16
5.10.3 Requirements . 16
5.11 Endurance . 16
5.11.1 Test conditions – Endurance current test (applies to inductors with a
mass < 5 g only) . 16
5.11.2 Test conditions – Endurance voltage test between terminations (applies
to inductors with more than one winding only) . 17

5.11.3 Final inspection, measurements and requirements. 17
5.12 Robustness of terminations . 17
5.12.1 General . 17
5.12.2 Test Ua1 – Tensile . 18
5.12.3 Test Ub – Bending . 18
5.12.4 Test Uc – Torsion . 18
5.12.5 Test Ud – Torque . 18
5.12.6 Test Ue – Robustness of terminations of SMD-components mounted on
PCB . 18
5.13 Vibration . 19
5.13.1 Test conditions . 19
5.13.2 Requirements . 19
5.14 Shock . 19
5.14.1 Test conditions . 19
5.14.2 Requirements . 20
5.15 Resistance to soldering heat . 20
5.16 Solderability (optional) . 20
5.16.1 General . 20
5.16.2 Preconditioning . 20
5.16.3 Test procedure . 20
5.16.4 Final inspection, measurements and requirements. 20
5.17 Rapid change of temperature (optional) . 20
5.18 Container sealing (if applicable) . 21
5.19 Climatic sequence (optional) . 21
5.19.1 General . 21
5.19.2 Dry heat . 21
5.19.3 Damp heat, cyclic, test Db, first cycle . 21
5.19.4 Cold. 21
5.19.5 Low air pressure . 21
5.19.6 Damp heat, cyclic, test Db, remaining cycles . 21
5.19.7 Final inspection, measurements and requirements. 21
5.20 Damp heat, steady state . 22
5.21 Passive flammability (optional) . 22
5.22 Glow wire (optional) . 22
5.23 Ball pressure (optional) . 23
5.24 Component solvent resistance . 23
5.25 Solvent resistance of marking . 23
Annex A (normative) Sampling plan . 24
Annex B (normative) Test schedule. 25
Annex C (normative) Declaration of design . 28
Annex D (normative) Clearance . 29
Annex E (normative) Creepage . 30
Annex F (normative) Fully insulated winding wires . 32
Annex X (informative) Cross-references for references to the previous edition of this
document . 33
Bibliography . 35

Figure 1 – Relation between ambient temperature and applied current . 10

– 4 – IEC 60938-2:2021 © IEC 2021

Table 1 – Test voltages . 14
Table 2 – Force for tensile stress on terminations . 18
Table 3 – Torque . 18
Table 4 – Acceleration . 19
Table 5 – Sweep cycles . 19
Table 6 – Preferred severities . 20
Table 7 – Severities and requirements for passive flammability. 22
Table D.1 – Clearance distances . 29
Table E.1 – Creepage distances . 31
Table F.1 – FIW wires with their minimum test voltages . 32
Table X.1 – Cross-references . 33

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
FIXED INDUCTORS FOR ELECTROMAGNETIC
INTERFERENCE SUPPRESSION –
Part 2: Sectional specification on power line chokes

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
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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 60938-2 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 and its
Amendment 1:2006. This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) the test plan for performance testing has been removed; mandatory safety tests and optional
performance tests are listed in one test plan in Annex B;
b) requirements for Thyristor-Chokes have been withdrawn;
c) material requirements are harmonized with IEC 60939-3 and UL 60939-3;
d) AC chokes up to 1 000 V and DC chokes up to 1 500 V are now in the Scope.

– 6 – IEC 60938-2:2021 © IEC 2021
The text of this International Standard is based on the following documents:
FDIS Report on voting
40/2846/FDIS 40/2862/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.
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 detail at www.iec.ch/standardsdev/publications.
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.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under "http://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.
FIXED INDUCTORS FOR ELECTROMAGNETIC
INTERFERENCE SUPPRESSION –
Part 2: Sectional specification on power line chokes

1 Scope
This part of IEC 60938 applies to fixed inductors designed for electromagnetic interference
suppression, which will be connected to an AC mains or other supply with a nominal voltage
not exceeding 1 000 V AC RMS or 1 500 V DC with a nominal frequency not exceeding 400 Hz.
This sectional specification is restricted to fixed inductors for which safety tests are appropriate.
This implies that inductors specified according to this specification will either be connected to
mains supplies, when compliance with the mandatory tests of Annex A is necessary, or used in
other circuit positions where the equipment specification prescribes that some or all of these
safety tests are required.
The object of this document is to prescribe standard requirements for safety tests, preferred
ratings and characteristics, to select from IEC 60938-1 the appropriate methods of test and to
give general performance requirements for suppression 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 applies, including any
amendments.
IEC 60027 (all parts), Letter symbols to be used in electrical technology
IEC 60050 (all parts), International Electrotechnical Vocabulary (IEV)
IEC 60060-1, High-voltage test techniques – Part 1: General definitions and test requirements
IEC 60068-1, Environmental testing – Part 1: General and guidance
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 60068-2-21, Environmental testing – Part 2-21: Tests – Test U: Robustness of terminations
and integral mounting devices
IEC 60068-2-45, Basic environmental testing procedures – Part 2-45: Tests – Test XA and
guidance: Immersion in cleaning solvents
IEC 60317-0-7, Specifications for particular types of winding wires – Part 0-7: General
requirements – Fully insulated (FIW) zero-defect enamelled round copper wire

– 8 – IEC 60938-2:2021 © IEC 2021
IEC 60317-56, Specifications for particular types of winding wires – Part 56: Solderable fully
insulated (FIW) zero-defect polyurethane enamelled round copper wire, class 180
IEC 60335-1, Household and similar electrical appliances – Safety – Part 1: General
requirements
IEC 60617, Graphical symbols for diagrams (available at http://std.iec.ch/iec60617)
IEC 60664-1, Insulation coordination for equipment within low-voltage supply systems – Part 1:
Principles, requirements and tests
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
IEC 60851-5, Winding wires – Test methods – Part 5: Electrical properties
IEC 60938-1:2021, Fixed inductors for electromagnetic interference suppression – Part 1:
Generic specification
IEC 60938-2-2, Fixed inductors for electromagnetic interference suppression – Part 2-2: Blank
detail specification – Inductors for which safety tests are required (only)
CISPR 17, Methods of measurement of the suppression characteristics of passive EMC filtering
devices
ISO 80000-6, Quantities and units – Part 6: Electromagnetism
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60938-1 apply.
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

4 General requirements
4.1 General
Units, graphical symbols, letter symbols and terminology shall be taken from the following
publications whenever possible:
– IEC 60027 (all parts),
– IEC 60050 (all parts),
– IEC 60617,
– ISO 80000-6.
When further items are required, they shall be derived in accordance with the principles of the
documents listed above.
4.2 Preferred values of ratings and characteristics
4.2.1 Climatic categories
Electromagnetic interference suppression inductors covered by this specification are classified
into climatic categories according to the general rules given in IEC 60068-1. The lower and
upper category temperatures and the duration of the damp heat, steady state test shall be
selected from the following:
Lower category temperature: −65 °C, −55 °C, −40 °C, −25 °C and −10 °C.
Upper category temperature: +85 °C, +100 °C, +125 °C and +155 °C.
Duration of the damp heat, steady state test: 21 days and 56 days.
The severities for the cold and dry heat tests are the lower and upper category temperatures
respectively.
4.2.2 Nominal inductance and tolerance
Preferred values of nominal inductance are values chosen from the E6 series of preferred
values given in IEC 60063.
The preferred tolerances on inductance are as follows:
±30 %; −30 % / +50 %
4.2.3 Rated voltage U
R
Preferred values for rated voltages are:
• for AC inductors:
50 V, 125 V, 250 V, 300 V, 400 V, 440 V, 480 V, 600 V, 760 V, 800 V and 1 000 V.
• for DC inductors:
60 V, 160 V, 250 V, 500 V, 1 000 V and 1 500 V.
Electromagnetic interference suppression inductors are normally chosen to have their rated
voltage equal to or greater than the nominal voltage of the supply system to which they are to
be connected. It should, however, be borne in mind that the voltage of the system may rise up
to 10 % above the nominal voltage.
4.2.4 Rated temperature T
r
The rated temperature shall be given in the detail specification. It shall not be lower than +40 °C.

– 10 – IEC 60938-2:2021 © IEC 2021
4.2.5 Rated current I
r
The preferred values of rated current are selected from the R10 series of ISO 3.
The following Figure 1 shows the relation between applied current and ambient temperature.

Figure 1 – Relation between ambient temperature and applied current
If not stated otherwise in the detail specification, a linear derating of applied current over
ambient temperature is assumed up to zero current at the upper category temperature T .
C
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 upon 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 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, which is mandatory for the application of the vibration and shock tests.
The design of the inductor may 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 the bump, 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 sectional
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 for power line applications
Insulated inductors may be built either with housing or with isolated wires where the isolation
provides basic or reinforced 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.
Fully insulated winding wires (FIW) shall comply by certificate with IEC 60851-5, IEC 60317-0-7
and IEC 60317-56. They may be applied maximum for insulation class F. FIW wires are chosen
from Table F.1 to have a minimum dielectric test voltage to withstand the voltage test B or C
with the test voltage defined in Table 1.
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 according to IEC 60695-11-10,
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 according to the relevant specifications shall be prescribed in the detail
specification. Deviations from these requirements shall be listed separately and the reason for
it stated specifically in the detail specification.
The information given in the marking is normally selected from the following list; the relative
importance of each item is indicated by its position in the list:
1) manufacturer's name or trade mark;
2) manufacturer's type designation;
3) recognized approval mark;
4) nominal inductance and its tolerance;
5) rated voltage;
6) rated current;
7) identification of terminations or circuit diagram;
8) rated temperature;
9) climatic category;
10) year and month or week of manufacture, maybe in code form;
11) reference to the detail specification.

– 12 – IEC 60938-2:2021 © IEC 2021
Marking of the inductor may be omitted when the manufacturer considers that there is
insufficient space, and this fact is recorded in the detail specification. When present, the
marking shall be sufficient to provide a clear identification of the inductor. Any duplication of
information in the marking on the inductor should be avoided.
The packaging containing the inductors shall be clearly marked with all the information listed
above except 7) identification of terminations or circuit diagram. Any additional marking shall
be so applied that no confusion can arise.
The marking information may be applied as QR Code.
5 Safety tests for approval
5.1 General
5.1.1 Approval on the basis of the fixed sample size procedures
This document covers a procedure for qualification approval tests. A test procedure is given
with mandatory safety tests and optional tests. Not all mandatory safety tests may be applicable
on every type of inductors as prescribed by the detail specification. Optional performance tests
shall be performed, if required in the detail specification.
Prior to the approval testing for safety tests only, it is necessary to submit to the certification
body a declaration of design (see Annex C) registering essential data and basic design details
of the inductors for which approval is sought. IEC 60938-2-2 provides a blank detail
specification for safety tests only. IEC 60938-2-1 provides a blank detail specification including
optional performance tests.
The complete series of tests is required for approval of a series of structurally similar inductors
of one rated voltage.
The tests of each group shall be carried out in the order given. The whole sample shall be
subjected to the tests of group 0 and then divided for the other groups. Non-conforming items
found during the tests of group 0 shall not be used for the other groups.
"One non-conforming item" is counted when an inductor has not satisfied the whole or part of
the tests of a group. The approval is granted when the number of non-conformances does not
exceed the specified number of permissible non-conforming items for each group or subgroup
and the total number of permissible non-conformances indicated in Annex A.
Annex A and Annex B together form the fixed sample size test schedule, for which Annex A
describes the details for the sampling and permissible non-conforming items for the different
tests or groups of tests. The conditions of tests and requirements for the fixed-sample-size test
schedule shall be identical to those prescribed in the detail specification.
5.1.2 Structurally similar inductors
Inductors are structurally similar when for their range of inductance values they have the
following common characteristics:
a) essentially the same materials;
b) similar design features and manufacturing techniques;
c) same rated voltage;
5.1.3 Sampling
Each rated voltage shall be separately qualified. The total number of inductors of each rated
voltage to be tested in each group is given in Annex A. For each rated voltage, the sample shall
contain equal numbers of specimens of the highest and lowest inductance and the highest and
lowest rated current in the range to be qualified. Where only one inductance value or rated
current value is involved, the total number of inductors shall be tested.
Spare specimens are permitted as follows:
a) one per inductance/rated current combination which may be used to replace the permitted
non-conforming items in group 0;
b) one per inductance/rated current combination which may be used as replacements for
specimens lost due to incidents not attributable to the manufacturer or the test sequence;
c) the remainder of the spares may be required if it is necessary to repeat any test solderability
or resistance to soldering heat;
d) spares may be kept at the premises of the manufacturer instead of being sent to the testing
station;
The numbers of samples given in group 0 assume that all groups are applicable. If this is not
the case, numbers may be reduced accordingly.
When additional groups are introduced into the qualification approval test schedule, the number
of specimens required for group 0 shall be increased by the same number as that required for
the additional groups.
Re-qualification tests according to Annex B may be required by the certification body when a
change of the design as given in Annex C is intended. The certification body will be informed
about the intended change(s) and decide whether re-qualification tests have to be performed.
5.2 Standard atmospheric conditions
Refer to 5.2 of IEC 60938-1:2021 without changes.
5.3 Visual examination
5.3.1 Dimensions (gauging)
The condition, workmanship and finish shall be satisfactory as checked by visual examination.
Marking shall be legible and shall conform to the requirements of the detail specification. The
dimensions indicated in the detail specification and being suitable for gauging shall be checked.
They shall comply with the values prescribed in the detail specification.
5.3.2 Dimensions (detail)
For mains 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 Annex D and Annex E.
Compliance shall be checked by measurement of clearance and creepage distances according
to the rules laid down in IEC 60335-1 or IEC 60664-1. Additional requirements may be
necessary for special-use inductors. Potting or sealing materials appear in lieu of clearance.
Instead of fulfilling requirements for clearance and creepage inside inductors, the windings may
be insulated e.g. by potting or insulation sleeves or the windings might be built from insulated
wires, e.g. TIW, FIW-wires, PVC-isolated wires, or the like.

– 14 – IEC 60938-2:2021 © IEC 2021
As in many cases, only clearance distances can be properly measured, the design of the
inductor shall assure that the according creepage distance requirements are fulfilled, if the
clearance is assured.
All other dimensions shall comply with the values prescribed in the detail specification.
5.4 Insulation resistance
Refer to 5.4 of IEC 60938-1:2021 with the following details:
a) the measuring voltage is to be used according to Table 2 of IEC 60938-1:2021;
b) the method of applying the test voltage for test C shall be the foil method;
c) the measurement time shall be 60 s;
d) no special precautions unless stated otherwise in the detail specification;
e) no correction factors unless stated otherwise in the detail specification;
f) standard atmospheric conditions unless stated otherwise in the detail specification;
g) the minimum value of insulation resistance with tests A, B and C shall be 6 MΩ.
5.5 Voltage test
Refer to 5.5 of IEC 60938-1:2021 with the following details:
a) the test voltage to be applied to mains inductors is given in the following Table 1 for basic
insulation. For reinforced insulation, the test voltages for Tests B, C and D are doubled.
Table 1 – Test voltages
Test B – Internal insulation
Inductors Test A* between Test C – External insulation
for terminations Test D** – Between windings
and core
AC 3 U V AC 2 U + 1 500 V AC
R R
with a minimum of 350 V AC with a minimum of 2 000 V AC
or
4,3 U V DC
R
with a minimum of 500 V DC
DC 2,2 U V AC 2 U + 1 500 V DC
R R
with a minimum of 350 V AC
or
3 U V DC
R
with a minimum of 500 V DC
* Applies only to inductors with more than one winding.
** Test required only if the core can be mounted to other metal parts over basic or
reinforced insulation
b) the method of applying the test voltage for test C shall be the foil method;
c) for approval testing, the full test voltage shall be applied for 1 min. For routine tests, the
detail specification may specify a shorter time, typically 1 s;
d) for routine tests AC or DC test voltages may be applied regardless whether AC or DC
inductors are tested.
The test time shall begin when the test voltage is reached. Repetition of the voltage proof test
may damage the inductor.
5.6 Inductance
Unless otherwise stated in the detail specification, the following measuring conditions apply:
a) the measuring frequency shall be chosen from the following:
1 MHz ± 20 % for L ≤ 10 µH
100 kHz ± 20 % for 10 µH < L ≤  1 mH
10 kHz ± 20 % for  1 mH < L ≤ 50 mH
50 Hz to 120 Hz for L > 50 mH

b) the measuring current shall be 0,1 mA ± 10 %. For some inductance values, it may be
desirable to use other current, voltage or frequency. The values of current, voltage and
frequency shall be given in the detail specification.
5.7 Line resistance
Line resistanc
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