IEC 60938-2:1999+AMD1:2006 CSV

INTERNATIONAL IEC
STANDARD 60938-2
QC 280100
Edition 2.1
2006-11
Edition 2:1999 consolidated with amendment 1:2006
Fixed inductors for electromagnetic
interference suppression –
Part 2:
Sectional specification
Reference number
IEC 60938-2:1999+A1:2006(E)
Publication numbering
As from 1 January 1997 all IEC publications are issued with a designation in the
60000 series. For example, IEC 34-1 is now referred to as IEC 60034-1.

Consolidated editions
The IEC is now publishing consolidated versions of its publications. For example,

edition numbers 1.0, 1.1 and 1.2 refer, respectively, to the base publication, the
base publication incorporating amendment 1 and the base publication incorporating
amendments 1 and 2.
Further information on IEC publications
The technical content of IEC publications is kept under constant review by the IEC,
thus ensuring that the content reflects current technology. Information relating to
this publication, including its validity, is available in the IEC Catalogue of
publications (see below) in addition to new editions, amendments and corrigenda.
Information on the subjects under consideration and work in progress undertaken
by the technical committee which has prepared this publication, as well as the list
of publications issued, is also available from the following:
• IEC Web Site (www.iec.ch)
• Catalogue of IEC publications
The on-line catalogue on the IEC web site (http://www.iec.ch/searchpub/cur_fut.htm)
enables you to search by a variety of criteria including text searches, technical
committees and date of publication. On-line information is also available on
recently issued publications, withdrawn and replaced publications, as well as
corrigenda.
• IEC Just Published
This summary of recently issued publications (http://www.iec.ch/online_news/
justpub/jp_entry.htm) is also available by email. Please contact the Customer
Service Centre (see below) for further information.
• Customer Service Centre
If you have any questions regarding this publication or need further assistance,
please contact the Customer Service Centre:

Email: custserv@iec.ch
Tel: +41 22 919 02 11
Fax: +41 22 919 03 00
INTERNATIONAL IEC
STANDARD 60938-2
QC 280100
Edition 2.1
2006-11
Edition 2:1999 consolidated with amendment 1:2006
Fixed inductors for electromagnetic
interference suppression –
Part 2:
Sectional 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
CN
Commission Electrotechnique Internationale

International Electrotechnical Commission
МеждународнаяЭлектротехническаяКомиссия
For price, see current catalogue

– 2 – 60938-2 © IEC:1999+A1:2006(E)

CONTENTS
FOREWORD.4

1 General .6

1.1 Scope.6

1.2 Object .6

1.3 Normative references .6

1.4 Information to be given in a detail specification .7

1.5 Definitions .8

1.6 Marking .8

2 Preferred ratings and characteristics.8
2.1 Climatic categories .8
2.2 Values of ratings.9
3 Quality assessment procedures .9
3.1 Primary stage of manufacture .9
3.2 Structurally similar inductors .9
3.3 Certified records of released lots .10
3.4 Qualification approval .10
3.5 Quality conformance inspection .14
4 Test and measurement procedures .14
4.1 Visual examination and check of dimensions.14
4.2 Voltage proof.15
4.3 Insulation resistance.15
4.4 Inductance.16
4.5 DC line resistance .16
4.6 Robustness of terminations.16
4.7 Resistance to soldering heat.16
4.8 Solderability.16
4.9 Rapid change of temperature.16
4.10 Vibration.17
4.11 Bump .17
4.12 Shock.18
4.13 Container sealing.18
4.14 Climatic sequence .18
4.15 Damp heat, steady state .19
4.16 Temperature rise (applies only to inductors with a mass >5 g).19
4.17 Impulse voltage (applies to inductors with more than one winding) .20

4.18 Endurance.21
4.19 Passive flammability (if applicable) .22
4.20 Component solvent resistance (if applicable) .22
4.21 Solvent resistance of marking (if applicable) .22

Annex A (normative) Test schedule for safety tests only approval.23
Annex B (normative) Test schedule for safety tests and performance tests
for qualification approval, assessment level D .26
Annex C (normative) Example of a suitable circuit for the endurance test voltage .31
Annex D (normative) Declaration of design (confidential to the manufacturer
and the certification body) .32
Annex E (normative) Test methods for thyristor electromagnetic
interference suppression inductors .33

60938-2 © IEC:1999+A1:2006(E) – 3 –

Figure C.1 – Endurance test circuit.31

Figure E.1 – Test circuit for temperature rise.33

Figure E. 2 – Test circuit for interference voltage attenuation.34

Table 1 – Sampling plan for safety tests only.12

Table 2 – Sampling plan for safety tests and performance tests, assessment level D .13

Table 3 – Measuring points .15

Table 4 – Acceleration.17

Table 5 – Sweep cycles.17
Table 6 – Preferred severities .18

– 4 – 60938-2 © IEC:1999+A1:2006(E)

INTERNATIONAL ELECTROTECHNICAL COMMISSION

____________
FIXED INDUCTORS FOR ELECTROMAGNETIC

INTERFERENCE SUPPRESSION –
Part 2: Sectional 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 60938-2 has been prepared by IEC technical committee 40:
Capacitors and resistors for electronic equipment.
This consolidated version of IEC 60938-2 consists of the second edition (1999) [documents
40/1111/FDIS and 40/1137/RVD] and its amendment 1 (2006) [documents 40/1603/CDV and
40/1700A/RVC].
The technical content is therefore identical to the base edition and its amendment and has
been prepared for user convenience.
It bears the edition number 2.1.
A vertical line in the margin shows where the base publication has been modified by
amendment 1.
The QC number that appears on the front cover of this publication is the specification number
in the IEC Quality Assessment System for Electronic Components (IECQ).

60938-2 © IEC:1999+A1:2006(E) – 5 –

Annexes A, B, C, D and E form an integral part of this standard.

The committee has decided that the contents of the base publication and its amendments will
remain unchanged until the maintenance result date indicated on the IEC web site under
"http://webstore.iec.ch" in the data related to the specific publication. At this date,

the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or

• amended.
A bilingual version of this publication may be issued at a later date.

– 6 – 60938-2 © IEC:1999+A1:2006(E)

FIXED INDUCTORS FOR ELECTROMAGNETIC

INTERFERENCE SUPPRESSION –
Part 2: Sectional specification

1 General
1.1 Scope
This International Standard applies to fixed inductors designed for electromagnetic interference
suppression and which fall within the scope of the generic specification, IEC 60938-1. It 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 table 1 is necessary, or used in other circuit positions
where the equipment specification prescribes that some or all of these safety tests are required.
This standard applies to fixed inductors which will be connected to an a.c. mains or other
supply with a nominal voltage not exceeding 1 000 V a.c. (r.m.s.) or d.c. between conductors
and with a nominal frequency not exceeding 400 Hz.
1.2 Object
The object of this standard is to prescribe standard requirements for safety tests and standard
ratings and characteristics, to select from IEC 60938-1 the appropriate methods of test and to
give general performance requirements for suppression inductors. Test severities and
performance requirements prescribed in detail specifications referring to this sectional
specification shall be of equal or higher performance level. In addition, the minimum require-
ments for safety tests specified herein always apply.
1.3 Normative references
Les documents de référence suivants sont indispensables pour l'application du présent
document. Pour les références datées, seule l'édition citée s'applique. Pour les références non
datées, la dernière édition du document de référence s'applique (y compris les éventuels
amendements).
IEC 60060-1:1989, High-voltage test techniques – Part 1: General definitions and test requirements
IEC 60063:1963, Preferred number series for resistors and capacitors
Amendment 1 (1967)
Amendment 2 (1977)
IEC 60085:1984, Thermal evaluation and classification of electrical insulation
IEC 60279:1969, Measurement of the winding resistance of an a.c. machine during operation at
alternative voltage
IEC 60938-1:1999, Fixed inductors for electromagnetic interference suppression – Part 1:
Generic specification
ISO 3:1973, Preferred numbers – Series of preferred numbers
CISPR 16-1-1:2003, Specification for radio disturbance and immunity measuring apparatus and
methods – Part 1-1: Radio disturbance and immunity measuring apparatus – Measuring
apparatus
60938-2 © IEC:1999+A1:2006(E) – 7 –

1.4 Information to be given in a detail specification

1.4.1 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 in 1.8 of the

detail specification and indicated in the test schedules, for example by an asterisk.

NOTE The information given in 1.4.2 may, for convenience, be presented in tabular form.

The information given in 1.4.2 to 1.4.5 shall be given in each detail specification and the values
quoted shall preferably be selected from those given in the appropriate clause of this sectional
specification.
1.4.2 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.
Normally 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 as will adequately describe the inductor. When the inductor is not
designed for use on printed boards, this shall be clearly stated in the detail specification.
1.4.3 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, bump 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.
1.4.4 Ratings and characteristics

The ratings and characteristics shall be in accordance with the relevant clauses of this
specification.
1.4.4.1 Additional characteristics may be listed, when they are considered necessary to
specify adequately the inductor for design and application purposes.
1.4.5 Marking
Deviations from 1.6 of this sectional specification, shall be specifically stated in the detail
specification.
– 8 – 60938-2 © IEC:1999+A1:2006(E)

1.5 Definitions
For the purpose of this International Standard, the definitions in IEC 60938-1 apply.

1.6 Marking
1.6.1 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:

a) manufacturer's name (or trade mark);

b) manufacturer's type designation;

c) recognized approval mark;
d) rated inductance and tolerance;
e) rated voltage;
f) rated current;
g) identification of terminations or circuit diagram;
h) rated temperature;
i) climatic category;
j) year and month (or week) of manufacture (this may be in code form);
k) reference to the detail specification.
1.6.2 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.
1.6.3 The packaging containing the inductor(s) shall be clearly marked with all the information
listed in 1.6.1, except g).
1.6.4 Any additional marking shall be so applied that no confusion can arise.
2 Preferred ratings and characteristics
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 and 56 days.
The severities for the cold and dry heat tests are the lower and upper category temperatures
respectively.
60938-2 © IEC:1999+A1:2006(E) – 9 –

2.2 Values of ratings
2.2.1 Rated inductance and tolerance

Preferred values of rated inductance are values chosen from the E 6 series of preferred values

given in IEC 60063.
The preferred tolerances on rated inductance are as follows:

±30 %; –30 %/+50 %.
2.2.2 Rated voltage (U )
R
Preferred values for rated voltages are:
AC inductors: 50 V, 125 V, 250 V, 400 V, 440 V, 480 V and 760 V.
DC inductors: 50 V, 160 V, 250 V and 500 V.
NOTE 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.
2.2.3 Category voltage (U )
C
The category voltage is equal to the rated voltage, unless otherwise stated in the detail
specification.
2.2.4 Rated temperature
The rated temperature shall not be lower than +40 °C.
2.2.5 Rated current
The preferred values of rated current are selected from the R10 series of ISO 3.
2.2.6 Passive flammability
When specified, the minimum category of passive flammability permitted is category C.
3 Quality assessment procedures

3.1 Primary stage of manufacture
See 3.2 of IEC 60938-1.
3.2 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.
– 10 – 60938-2 © IEC:1999+A1:2006(E)

3.3 Certified records of released lots

When certified test records are requested by a purchaser, they shall be specified in the detail

specification.
3.4 Qualification approval
The procedures for qualification approval testing for structurally similar inductors are given

in 3.4 of IEC 60938-1.
3.4.1 Qualification approval on the basis of the fixed sample size procedures

3.4.1.1 Sampling
This standard covers procedures for qualification approval tests only. Two alternative test
procedures are given, namely the full test procedure covering both safety tests and
performance requirements, and a restricted test procedure covering safety tests.
Table 1 and annex A form the schedule limited to tests for safety tests only approval. Prior to
the approval testing for safety tests only it is necessary to submit to the certification body a
declaration of design (annex D) registering essential data and basic design details of the
inductors for which approval is sought.
Table 2 and annex B form the full schedule for safety tests and performance approval.
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 table 1 or 2. 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 as stated in table 1 or 2 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 according
to the provisions of note 1 to table 1 or 2;
d) spares may be kept at the premises of the manufacturer instead of being sent to the testing station.
The number of samples given in group 0 assume that all groups are applicable. If this is not so
the 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.

60938-2 © IEC:1999+A1:2006(E) – 11 –

3.4.1.2 Tests
The complete series of tests specified in either table 1 or 2 is required for the 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 table 1 or 2.
NOTE Table 1 and annex A or table 2 and annex B together form the fixed sample size test schedule, for which
table 1 or 2 includes the details for the sampling and permissible non-conforming items for the different tests or
groups of tests, whereas annexes A or B together with the details of test contained in clause 4 give a complete
summary of test conditions and performance requirements and indicate where, for example for the test method or
conditions of test, a choice has to be made in the detail specification. The conditions of test and performance
requirements for the fixed sample size test schedule shall be identical to those prescribed in the detail
specification.
– 12 – 60938-2 © IEC:1999+A1:2006(E)

Table 1 – Sampling plan for safety tests only

Group Test Subclause Number of specimens Number of permissible

of this tested per rated voltage non-conforming items

publication and for each mass per rated voltage

group (2)
Per group Total
n c c
0 Visual examinations 4.1
Line resistance 4.5 1
Inductance 4.4 40/22/10/5
Voltage proof 4.2
Insulation resistance 4.3
Spares 4/2/2/1
1A Dimensions (detail) 4.1.2
Creepage distances and
clearances 4.1.2 10/6/2/1 0
Robustness of terminations 4.6
Resistance to soldering
heat (1) 4.7
Component solvent
resistance (if applicable) (5) 4.20
2 Damp heat, steady state 4.15 18/10/4/2 0 0
Temperature rise (3) 4.16
3A or or
Endurance current (4) 4.18
3B Impulse voltage (7)(8) 4.17 12/6/4/2 0
Endurance voltage 4.18
between line termina-
tions (7)
4 Passive flammability (5) 4.19 see 4.19 0
NOTES to tables 1 and 2:
NOTE 1 If applicable.
NOTE 2 The number of specimens indicated relate to the mass limits as follows:
≤5 g
>5 g and ≤250 g
>250 g and ≤1 500 g
>1 500 g respectively.
Where a range is qualified which contains inductors within more than one of the mass classifications listed
above, the number of specimens selected shall be that for the classification in which the majority of the values

in the range fall.
The numbers in group 0 exclude the numbers of specimens required for group 4.
NOTE 3 For inductors with a weight >5 g only.
NOTE 4 For inductors with a weight ≤5 g only.
NOTE 5 If required in the detail specification.
NOTE 6 Whichever is required in the detail specification.
NOTE 7 Applicable to inductors with more than one winding of different polarity.
NOTE 8 Applicable to inductors with earthed metal case, not connected to one of the line terminations.
NOTE 9 If one non-conforming item is obtained, all tests of the group shall be repeated on a new sample and
then no further non-conforming items are permitted. The non-conforming item obtained in the first sample shall
be counted for the total non-conforming items permitted in the sixth column. Repetition of tests is permitted in
one group only.
60938-2 © IEC:1999+A1:2006(E) – 13 –

Table 2 – Sampling plan for safety tests and performance tests,
assessment level D
Group Test Subclause Number of Number of permissible

of this specimens tested per non-conforming items per

publication qualification (2) qualification (2)

Per group Total
n c c
0 Dimensions (gauging) 4.1
Visual examinations 4.1
DC line resistance 4.5
Inductance 4.4 76/48/28/16 2/1/1/1
Voltage proof 4.2
Insulation resistance 4.3
Spares 24/15/10/5
Dimensions (detail) 4.1.2
Creepage distances and 4.1.2
clearances
Robustness of terminations 4.6
1A
Resistance to soldering
heat (1) 4.7 10/6/2/1 0 (9)
Component solvent
resistance (5) 4.20
Solderability (1) 4.8
Solvent resistance of
marking (5) 4.21
Rapid change of
1B
temperature 4.9 18/12/6/3 0 (9) 1/1/1/0
Vibration 4.10
Bump or shock (6) 4.11 or
4.12
1 Container sealing (5) 4.13 28/18/8/4 0 (9)
Climatic sequence 4.14
2 Damp heat, steady state 4.15 16/10/8/4 0 (9)
Temperature rise (3) 4.16
3A or or 12/8/4/4 0 (9)
Endurance current (4) 4.18
3B Impulse voltage (7)(8) 4.17
Endurance voltage between 4.18 20/12/8/4 0

line terminations (7)
4 Passive flammability (5) 4.19 See 4.19 0
See notes to tables 1 and 2 at the bottom of table 1.

– 14 – 60938-2 © IEC:1999+A1:2006(E)

3.5 Quality conformance inspection

3.5.1 Formation of inspection lots

a) Groups A and B inspection
These tests shall be carried out on a lot-by-lot basis using sampling plans appropriate to

the given assessment level specified in the relevant blank detail specification.

Manufactured lots of separately identified inductors may be aggregated into inspection lots
formed for such tests as are relevant to structural similarities between those manufactured lots.

b) Group C inspection
– Safety tests only approval
Re-qualification tests according to annex A may be required by the certification body when
a change of the design as given in annex D is intended.
The certification body will be informed about the intended change(s) and decide whether re-
qualification tests have to be performed.
– Full safety tests and performance approval
Periodic tests according to annex B shall be carried out at the periodicities and on the
numbers of specimens appropriate to the given assessment level specified in the relevant
blank detail specification. In order to reduce the number of specimens required to carry out
any single complete periodic test, the manufacturer may elect to have the tests of more
than one subgroup carried out sequentially on the same specimens.
The specimens shall be representative of the inductors manufactured during each period.
In subsequent periods other inductors in the approved range in production shall be tested
with the aim of covering the whole range of the approval.
3.5.2 Test schedule
– Safety tests only approval
The test schedule for the lot-by-lot and periodic tests or criteria for re-qualification is given
in table 4 of the relevant blank detail specification, IEC 60938-2-2.
– Full safety tests and performance approval
The test schedule for the lot-by-lot and periodic tests for quality conformance inspection is
given in table 4 of the relevant blank detail specification, IEC 60938-2-1.
3.5.3 Delayed delivery
When according to the procedures in 3.5.2 of IEC 60938-1, re-inspection has to be made,
insulation resistance shall be checked as specified in group A inspection and solderability shall

be checked according to group B inspection.
4 Test and measurement procedures
4.1 Visual examination and check of dimensions
Visual examination and check of dimensions shall be in accordance with 4.4 of IEC 60938-1.
4.1.1 Dimensions (gauging)
The dimensions indicated in the detail specification as being suitable for gauging shall be
checked, and shall comply with the values prescribed in the detail specification.
When applicable, checks shall be made in accordance with IEC 60294.

60938-2 © IEC:1999+A1:2006(E) – 15 –

4.1.2 Dimensions (detail)
Creepage distances and clearances shall comply with the values prescribed in table 2 of

IEC 60938-1. All other dimensions shall comply with the values prescribed in the detail

specification.
4.2 Voltage proof
See 4.6 of IEC 60938-1 with the following details:

a) the test voltage to be applied to mains inductors is given in table 3:

Table 3 – Measuring points
Test B – Internal insulation)
Test C – External insulation
Inductors for Test A between terminations*
Test D** – Between windings
and core
Alternating 4,3 U (d.c.) 2 U + 1 500 V (a.c.) with a minimum
R R
current
of 2 000 V (a.c.)
Direct current 3 U (d.c.) 2 U + 1 500 V (d.c.)
R R
* Applies only to inductors with more than one winding.
** Test not required for insulated or non-insulated and self-supporting mountable inductors.

b) the method of applying the test voltage for test C shall be given in the detail specification.
For qualification testing the foil method of 4.6.2.3 of IEC 60938-1, shall be used;
c) for qualification approval and periodic testing the full test voltage shall be applied for 1 min.
For quality conformance tests the detail specification may specify a shorter time;
d) for d.c. tests the charge and discharge current shall not exceed 0,05 A;
e) for d.c. tests the time constant R × C shall not exceed 1 s;
1 S
f) for qualification approval a.c. tests, the voltage shall be supplied from a transformer.
The voltage shall be raised from near zero to the test voltage at a rate not faster than
150 V/s. The test time shall begin at the moment the test voltage is reached. For quality
conformance tests, the detail specification may require the full test voltage to be applied
directly.
NOTE Attention is drawn to the fact that repetition of the voltage proof test may damage the inductor.
4.3 Insulation resistance
See 4.5 of IEC 60938-1 with the following details:
a) the measuring voltage shall be as prescribed in 4.5.2 of IEC 60938-1;
b) the method of applying the test voltage for test C may be any of the methods specified
in 4.5.2.1, 4.5.2.2 and 4.5.2.3 of IEC 60938-1. For qualification testing the foil method
of 4.5.2.1 shall be used;
c) the minimum value of insulation resistance with tests A, B and C shall be 6 000 MΩ.

– 16 – 60938-2 © IEC:1999+A1:2006(E)

4.4 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 currents or frequencies. The values of the current or frequency shall
be given in the detail specification.
4.5 DC line resistance
Using a d.c. 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 prescribed in the detail specification. The detail specification may specify
precise points of connection between the terminals and the measuring instrument.
4.6 Robustness of terminations
See 4.9 of IEC 60938-1.
4.7 Resistance to soldering heat
See 4.10 of IEC 60938-1 with the following details:
Not applicable to inductors having leads with insulation length greater than 10 mm or with
snap-on terminations.
4.7.1 Conditions
No pre-drying.
4.7.2 Final inspection, measurements and requirements
The inductors shall be visually examined and measured and shall meet the requirements in
annex A or B.
4.8 Solderability
See 4.11 of IEC 60938-1 with the following details:
4.8.1 When the solder globule method is used the soldering time shall be less than 3 s.
4.8.2 The requirements are given in annex B.
4.9 Rapid change of temperature
See 4.12 of IEC 60938-1 with the following details:

60938-2 © IEC:1999+A1:2006(E) – 17 –

4.9.1 Number of cycles: 5.
Duration of exposure at the temperature limits:

– 1 h for mass group <250 g;
– 3 h for mass group ≥250 g.
4.10 Vibration
See 4.13 of IEC 60938-1 with the following details:

4.10.1 One of the following severities of test Fc, as specified in the detail specification:
Displacement or acceleration, whichever is the lower acceleration as specified in table 4.
Table 4 – Acceleration
Mass group Amplitude or acceleration
(whichever is the lower
acceleration)
>5 g 0,35 mm or 49 m/s (5 g)
0,75 mm or 98 m/s (10 g)
≤5 g
Over one of the following frequency ranges: 10 Hz to 55 Hz, 10 Hz to 500 Hz, 10 Hz to 2 000 Hz.
The total number of sweep cycles to be applied in relation to the frequency ranges are as
specified in table 5.
Table 5 – Sweep cycles
Frequency Total number of
Hz sweep cycles
10 to 55
3 × 24
10 to 500
3 × 10
10 to 2 000
3 × 8
The detail specification shall specify the frequency range and shall also prescribe the mounting

method to be used.
4.10.2 Final inspection and requirements
The inductors shall be visually examined and shall meet the requirements in annex B.
4.11 Bump
See 4.14 of IEC 60938-1 with the following details:
4.11.1 The detail specification shall state whether the bump or the shock test applies.

– 18 – 60938-2 © IEC:1999+A1:2006(E)

One of the following severities shall be specified in the detail specification:

Total number of bumps: 1 000 or 4 000

2 2
Acceleration: 390 m/s (40 g) or 98 m/s (10 g)

Pulse duration: 6 ms 16 ms
The detail specification shall also prescribe the mounting method to be used.

4.11.2 Final inspection and requirements

The inductors shall be visually examined and meet the requirements in annex B.
4.12 Shock
See 4.15 of IEC 60938-1 with the following details:
4.12.1 The detail specification shall state whether the bump or the shock test applies.
4.12.2 The detail specification shall state which of the preferred severities in table 6 applies.
Pulse shape: half-sine.
Table 6 – Preferred severities
Peak acceleration Corresponding duration of
the pulse
m/s (g)
ms
294 (30) 18
490 (50) 11
981 (100) 6
The detail specification shall also prescribe the mounting method to be used.
4.12.3 Final inspection, measurements and requirements
The inductors shall be visually examined and measured and shall meet the requirements in
annex B.
4.13 Container sealing
See 4.16 of IEC 60938-1.
4.14 Climatic sequence
See 4.17 of IEC 60938-1 with the following details:
4.14.1 Initial measurements
Not required.
4.14.2 Dry heat
No measurements are required at the upper category temperature.

60938-2 © IEC:1999+A1:2006(E) – 19 –

4.14.3 Damp heat, cyclic, test Db, first cycle

See 4.17.3 of IEC 60938-1.
4.14.4 Cold
No measurements are required at the lower category temperature.

4.14.5 Low air pressure
See 4.17.5 of IEC 60938-1 with the following details:

If required in the detail specification, the test shall be made at a room temperature of 15 °C
to 35 °C and a pressure of 8,0 kPa, unless otherwise stated in the detail specification. The
duration of the tests shall be 1 h.
During and after the test there shall be no evidence of permanent breakdown, flashover, or
harmful deformation of the case.
4.14.6 Damp heat, cyclic, test Db, remaining cycles
See 4.17.6 of IEC 60938-1.
4.14.7 Final inspection, measurements and requirements
After recovery the inductors shall be visually examined and measured and shall meet the
requirements given in annex B.
4.15 Damp heat, steady state
See 4.18 of IEC 60938-1 with the following details:
4.15.1 Final inspection, measurements and requirements
After recovery the inductors shall be visually examined and measured and shall meet the
requirements of annex A or B.
4.16 Temperature rise (applies only to inductors with a mass >5 g)
The purpose of the test is to show that when the relevant temperature rise is added to the rated
temperature the maximum working temperature of the internal insulation (according to the
requirements of IEC 60085), or of the inductive element(s) is not exceeded.

See 4.19 of IEC 60938-1 with the following details:
4.16.1 Test method
The inductor shall be placed in a chamber maintained at an ambient temperature as close as
possible to the rated temperature. The rated a.c. current or a d.c. current equal to the r.m.s.
value of the rated a.c. current shall be applied.
After thermal equilibrium has been reached the internal temperature of the inductor shall be
determined by evaluating the change of resistance of the inductor series resistance.

– 20 – 60938-2 © IEC:1999+A1:2006(E)

The internal temperature T at thermal equilibrium shall be calculated from the measured
resistance R between the input and the output terminals at the temperature T and its

2 2
measured resistance R at the test chamber temperature at the start of the test T using the
1 1
formula:
R
T=+()235TT−(−T)− 235(for copper)
2 13 1
R
R
T=+()225TT−(−T)− 225(for aluminium)
2 13 1
R
where T is the temperature of the test chamber at the end of the test and T , T and T are
3 1 2 3
expressed in degrees Celsius.
Where other metals are used for the inductor windings the appropriate formula shall be stated
in the detail specification.
The resistance R is measured either after switching off the supply, or without interruption of
the supply by means of the superposition method, which consists of injecting into th
...