IEC 60939-1:2005

INTERNATIONAL IEC
STANDARD 60939-1
Second edition
2005-02
Passive filter units for electromagnetic
interference suppression –
Part 1:
Generic specification
Reference number
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INTERNATIONAL IEC
STANDARD 60939-1
Second edition
2005-02
Passive filter units for electromagnetic
interference suppression –
Part 1:
Generic specification
 IEC 2005  Copyright - all rights reserved
No part of this publication may be reproduced or utilized in any form or by any means, electronic or
mechanical, including photocopying and microfilm, without permission in writing from the publisher.
International Electrotechnical Commission, 3, rue de Varembé, PO Box 131, CH-1211 Geneva 20, Switzerland
Telephone: +41 22 919 02 11 Telefax: +41 22 919 03 00 E-mail: inmail@iec.ch Web: www.iec.ch
PRICE CODE
Commission Electrotechnique Internationale
V
International Electrotechnical Commission
Международная Электротехническая Комиссия
For price, see current catalogue

– 2 – 60939-1  IEC:2005(E)
CONTENTS
FOREWORD.4

1 General .6

1.1 Scope.6

1.2 Normative references .6

2 Technical data.7

2.1 Units, symbols and terminology .7

2.2 Terms and definitions .8
2.3 Preferred values.10
2.4 Marking .10
3 Quality assessment procedures.10
3.1 General .10
3.2 Primary stage of manufacture.11
3.3 Subcontracting .11
3.4 Structurally similar filters .11
3.5 Qualification approval procedures .12
3.6 Capability approval procedures .12
3.7 Rework and repair work.13
3.8 Release for delivery .14
3.9 Certified test records .14
3.10 Delayed delivery.14
3.11 Alternative test methods .14
3.12 Unchecked parameters.14
4 Test and measurement procedures.15
4.1 General .15
4.2 Standard atmospheric conditions.15
4.3 Drying .16
4.4 Visual examination and check of dimensions.16
4.5 Insulation resistance .17
4.6 Voltage proof.19
4.7 Insertion loss.22
4.8 Discharge resistance.22

4.9 Robustness of terminations .22
4.10 Resistance to soldering heat .24
4.11 Solderability .24
4.12 Rapid change of temperature .25
4.13 Vibration.25
4.14 Bump .25
4.15 Shock.25
4.16 Container sealing .26
4.17 Climatic sequence .26
4.18 Damp heat, steady state.27
4.19 Temperature rise.27
4.20 Current overload .28

60939-1  IEC:2005(E) – 3 –
4.21 Endurance.28

4.22 Charge and discharge test.28

4.23 Passive flammability.31

4.24 Active flammability .31

4.25 Solvent resistance of marking.31

4.26 Component solvent resistance.32

Figure 1 – Asymmetrical and symmetrical test circuit .9

Figure 2 – Examples of the application of Table 3.19
Figure 3 – Test circuit for d.c. test .20
Figure 4 – Relay circuit .29
Figure 5 – Thyristor circuit .29
Figure 6 – Voltage and current waveforms .30

Table 1 – Standard atmospheric conditions.16
Table 2 – DC voltage for insulation resistance .17
Table 3 – Measuring points.19
Table 4 – Force for wire terminations .23
Table 5 – Torque .23
Table 6 – Number of cycles .27
Table 7 – Categories of flammability .31

– 4 – 60939-1  IEC:2005(E)
INTERNATIONAL ELECTROTECHNICAL COMMISSION

___________
PASSIVE FILTER UNITS FOR ELECTROMAGNETIC

INTERFERENCE SUPPRESSION –
Part 1: Generic specification
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with an IEC Publication.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.

International Standard IEC 60939-1 has been prepared by IEC technical committee 40:
Capacitors and resistors for electronic equipment.
This second edition cancels and replaces the first edition published in 1988. This second
edition constitutes a technical revision.
The major changes that have been made between the first and the second edition are:
– Clause 3 has been updated in accordance with the usual practice in IEC TC 40 documents.
– Discharge resistance, current overload, passive flammability, active flammability, solvent
resistance of marking and component solvent resistance have been added to Clause 4,
test and measurement procedures.

NOTE Corrigendum 1 (2005-11) has been included in this copy. It constitutes a revision of the structure of
subclause 4.5, as well as an addition to subclause 4.10.3.

60939-1  IEC:2005(E) – 5 –
The text of this standard is based on the following documents:

FDIS Report on voting
40/1509/FDIS 40/1536/RVD
Full information on the voting for the approval of this standard can be found in the report on

voting indicated in the above table.

This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.

IEC 60939 consists of the following parts, under the general title Passive filter units for
electromagnetic interference suppression
Part 1: Generic specification
Part 2: Sectional specification: Test methods and general requirements
Part 2-1: Blank detail specification – Passive filter units for electromagnetic interference
suppression – Filters for which safety tests are required (Assessment level D/DZ)
Part 2-2: Blank detail specification – Passive filter units for electromagnetic interference
suppression – Filters for which safety tests are required (Safety tests only)

The committee has decided that the contents of this publication will remain unchanged until
the maintenance result date indicated on the IEC web site under "http://webstore.iec.ch" in
the data related to the specific publication. At this date, the publication will be
• reconfirmed;
• withdrawn;
• replaced by a revised edition, or
• amended.
A bilingual version of this publication may be issued at a later date.

– 6 – 60939-1  IEC:2005(E)
PASSIVE FILTER UNITS FOR ELECTROMAGNETIC

INTERFERENCE SUPPRESSION –
Part 1: Generic specification
1 General
1.1 Scope
This generic specification relates to passive filter units for electromagnetic interference sup-
pression for use within, or associated with, electronic or electrical equipment and machines.
Both single- and multi-channel filters within one enclosure are included within the scope of
this generic specification.
Filters constructed of capacitive elements where the inductance is inherent in the construction
of the filter are within the scope of this specification. Similarly, filters constructed of inductive
elements where the capacitance is inherent in the construction of the filter are also within the
scope of this generic specification. The manufacturer shall state whether a given component
is to be designed as a capacitor, an inductor or a filter.
The filter units within the scope of this generic specification are further distinguished as those
for which safety tests are appropriate (e.g. those connected to mains supplies) and those for
which such tests are not appropriate. A separate sectional specification covers the passive
filter units for which safety tests are appropriate.
This generic specification establishes standard terms, inspection procedures and methods of
test for use in sectional and detail specifications within the IECQ-CECC system for electronic
components.
1.2 Normative references
The following referenced documents are indispensable for the application of this document.
For dated references, only the edition cited applies. For undated references, the latest edition
of the referenced document (including any amendments) applies.
NOTE Components other than inductors and capacitors in the filter unit should fulfil requirements in the relevant
IEC Standard.
IEC 60027 (all parts), Letter symbols to be used in electrical technology

IEC 60050 (all parts), International Electrotechnical Vocabulary (IEV)
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: Tests – Tests A: Cold
IEC 60068-2-2, Environmental testing – Part 2: Tests – Tests B: Dry Heat
IEC 60068-2-6, Environmental testing – Part 2: Tests – Test Fc: Vibration (sinusoidal)
IEC 60068-2-13, Environmental testing – Part 2: Tests – Test M: Low air pressure

60939-1  IEC:2005(E) – 7 –
IEC 60068-2-14, Environmental testing – Part 2: Tests – Test N: Change of temperature

IEC 60068-2-17, Basic environmental testing procedures – Part 2: Tests – Test Q: Sealing

IEC 60068-2-20, Environmental testing – Part 2: Tests – Test T: Soldering

IEC 60068-2-21, Environmental testing – Part 2-21: Tests – Test U: Robustness of termina-

tions and integral mounting devices

IEC 60068-2-27, Environmental testing – Part 2: Tests – Test Ea and guidance: Shock

IEC 60068-2-29, Environmental testing – Part 2: Tests – Test Eb and guidance: Bump
IEC 60068-2-30, Environmental testing – Part 2: Tests – Test Db and guidance: Damp heat,
cyclic (12 + 12-hour cycle)
IEC 60068-2-45, Environmental testing – Part 2: Tests – Test XA and guidance: Immersion in
cleaning solvents
IEC 60068-2-78, Environmental testing – Part 2-78: Tests – Test Cab: Damp heat, steady
state
IEC 60085, Thermal evaluation and classification of electrical insulation
IEC 60294, Measurement of the dimensions of a cylindrical component having two axial
terminations.
IEC 60384-14: Fixed capacitors for use in electronic equipment – Part 14: Sectional
specification: Fixed capacitors for electromagnetic interference suppression and connection to
the supply mains
IEC 60410, Sampling plans and procedures for inspection by attributes
IEC 60695-2-2, Fire hazard testing – Part 2: Test methods – Section 2: Needle flame test
IEC QC 001002-3, IEC Quality assessment system for electronic components (IECQ) – Rules
of procedure – Part 3: Approval procedures
CISPR 17:1981, Methods of measurement of the suppression characteristics of passive radio
interference filters and suppression components
ISO 1000:1992, SI units and recommendations for the use of their multiples and of certain
other units
2 Technical data
2.1 Units, symbols and terminology
Units, graphical symbols, letter symbols and terminology shall, whenever possible, be taken
from the following publications:
– IEC 60027
– IEC 60050
– ISO 1000
– 8 – 60939-1  IEC:2005(E)
When further items are required they shall be derived in accordance with the principles of the

publications listed above.
2.2 Terms and definitions
For the purpose of the IEC 60939 series, the following terms and definitions apply.

2.2.1
type
group of components having similar design features, the similarity of their manufacturing

techniques enabling them to be grouped together either for qualification approval or for quality

conformance inspection, and generally covered by a single detail specification
NOTE Components described in several detail specifications may, in some cases, be considered as belonging to
the same type and may therefore be grouped together for approval and quality conformance inspection.
2.2.2
style
subdivision of a type, generally based on dimensional factors; a style may include several
variants, generally of a mechanical order
2.2.3
electromagnetic interference suppression filter unit (filter)
radio interference suppression filter unit
assembly of piece-parts and inductive, capacitive and resistive elements to be used for the
reduction of electromagnetic interference caused by electrical or electronic equipment, or
other sources
2.2.4
rated voltage
U
R
maximum r.m.s. operating voltage at rated frequency or the maximum d.c. operating voltage
which may be applied continuously to the terminations of the filter unit at any temperature
between the lower and the upper category temperatures
2.2.5
category voltage
U
C
maximum voltage which may be applied to a filter at its upper category temperature
2.2.6
lower category temperature
minimum ambient temperature for which the filter has been designed to operate continuously

2.2.7
upper category temperature
maximum ambient temperature for which the filter unit has been designed to operate
continuously
2.2.8
rated temperature
maximum ambient temperature at which a filter can carry its rated current
2.2.9
rated current
maximum r.m.s. operating current at rated frequency or maximum d.c. rating current which
allows continuous operation of the filter at the rated temperature, assigned by the
manufacturer for one or both of the following conditions:
a) free air (I );
RO
b) with a specified heat sink (I )
RH
60939-1  IEC:2005(E) – 9 –
2.2.10
rated capacitance
C
R
capacitance value for which a capacitor has been designed and which may be indicated

upon it
2.2.11
rated inductance
L
R
inductance value for which the inductor has been designed and which may be indicated upon it

2.2.12
insertion loss
ratio of the voltage before and after the insertion of the filter in the circuit as measured at the
terminations either with a symmetrical or an asymmetrical test circuit
NOTE It is normally expressed in decibels, when the insertion loss is 20 times the logarithm to base 10 of this
ratio.
2.2.13
asymmetrical test circuit
test circuit in which the filter under test is connected as a 3-terminal network, one terminal of
which is connected to earth
NOTE The signal is applied between the input terminal and earth, and the output is measured between the output
terminal and earth. There is a common (earth) connection between generator, filter and receiver (see Figure 1).
2.2.14
symmetrical test circuit
test circuit in which the filter under test is connected as a 4-terminal network
NOTE 1 The test signal applied to the two input terminals symmetrically about earth, i.e. equal in magnitude but
of opposite phase on the two terminals (see Figure 1). The output is measured between the other two terminals.
NOTE 2 It is usual to perform symmetrical tests using an asymmetrical generator and receiver with suitable
balance-to-unbalance transformers connected between them and the filter under test.
2.2.15
visible damage
visible damage which reduces the usability of the filter for its intended purpose

Filter Filter
under under
R
test test
R
Asymmetrical test circuit Symmetrical test circuit
IEC  256/05
Figure 1 – Asymmetrical and symmetrical test circuit
2.2.16
passive flammability
ability of a filter to burn with a flame as a consequence of the application of an external
source of heat
2.2.17
active flammability
ability of a filter to burn with a flame as a consequence of electrical loading

– 10 – 60939-1  IEC:2005(E)
2.3 Preferred values
Each sectional specification shall prescribe the preferred values appropriate to the subfamily

covered by that sectional specification.

2.4 Marking
2.4.1 General
The sectional specification shall indicate the identification criteria and other information to be

shown on the filters and the packing.

2.4.2 Coding
When coding is used for tolerance or date of manufacture, the method shall be selected from
those given in IEC 60062.
3 Quality assessment procedures
3.1 General
Before filters are qualified according to the procedures of this Clause, the manufacturer shall
obtain approval of his organisation following the provisions of IEC QC 001002-3.
Two methods are available for the approval of filters of assessed quality. These are qualifi-
cation approval and capability approval, both according to the provisions of IEC QC 001002-3.
For a given subfamily of filters, separate sectional specifications for qualification approval and
capability approval are necessary, and capability approval is therefore available only when a
relevant sectional specification has been published.
3.1.1 Applicability of qualification approval
Qualification approval is appropriate for a range of filters manufactured to similar design and
production processes and conforming to a published detail specification.
The programme of tests defined in the detail specification for the appropriate assessment and
performance levels applies directly to the filter range to be qualified, as prescribed in 3.5 and
the relevant sectional specification.
3.1.2 Applicability of capability approval
Capability approval is appropriate when filters based on common design rules are fabricated
by a group of common processes. It is particularly appropriate when filters are manufactured
to a user's specific requirements.
Under capability approval, detail specifications fall into the following three categories for:
3.1.2.1 Capability Qualifying Components (CQCs), including process validation test
vehicles
A detail specification shall be prepared for each CQC as agreed with the ONS. It shall identify
the purpose of the CQC and include all relevant test severities and limits.

60939-1  IEC:2005(E) – 11 –
3.1.2.2 Components for listing in the register of approvals (standard catalogue items)

When the manufacturer wants a filter covered by the capability approval procedure to be

listed in the IECQ Register of Approvals, a capability approval detail specification complying

with the blank detail specification shall be written. Such specifications shall be registered by

the IECQ and the component may be listed in IEC QC 001005: Register of Firms, Products

and Services Approved under the IECQ-CECC System.

3.1.2.3 Customer specified filters

The content of the detail specification (often known as a Customer Detail Specification CDS)

shall be by agreement between the manufacturer and customer in accordance with
IEC QC 001002-3.
Further information on these detail specifications is given in the relevant blank detail
specification.
Approval is given to a manufacturing facility on the basis of validated design rules, processes
and quality control procedures and the results of tests on capability qualifying components,
including any process validation test vehicles. See 3.6 and the relevant sectional specification
for further information.
3.2 Primary stage of manufacture
The primary stage of manufacture depends on the construction of the filter:
a) for filters constructed of capacitive elements where the inductance is inherent in the
capacitive elements or the construction of the filter, the primary stage of manufacture is
the same as for capacitor(s) of the same technology, as defined in the relevant fixed
capacitor sectional specification;
b) for filters constructed of inductive elements where the capacitance is inherent in the
inductive elements or the construction of the filter, the primary stage of manufacture is the
winding of the inductive element(s);
c) for filters which are assembled from capacitive and inductive elements, whether these
elements are bought-in or manufactured in-house, the primary stage of manufacture is the
manufacturer's evaluation of the capacitive, inductive or resistive elements. Evaluation of
capacitive, inductive or resistive elements may be further defined in the sectional
specification.
3.3 Subcontracting
The manufacturer shall not sub-contract the primary stage of manufacture or any subsequent

stage, except as follows:
– for a) in 3.2, the manufacturer may use capacitors released under the IECQ-CECC system;
– for b) in 3.2, the manufacturer may use inductors released under the IECQ-CECC system;
– for a), b) and c) in 3.2, painting and plating may be subcontracted.
3.4 Structurally similar filters
The grouping of structurally similar filters for qualification approval testing or for quality
conformance testing under qualification approval or capability approval shall be prescribed in
the relevant sectional specification.

– 12 – 60939-1  IEC:2005(E)
3.5 Qualification approval procedures

3.5.1 Eligibility for qualification approval

The manufacturer shall comply with 3.1.1 of IEC QC 001002-3.

3.5.2 Application for qualification approval

The manufacturer shall comply with 3.1.3 of IEC QC 001002-3.

3.5.3 Test procedure for qualification approval

One of the two following procedures shall be followed:
1) The manufacturer shall produce test evidence of conformance to the specification
requirements on three inspection lots for lot-by-lot inspection taken in as short a time as
possible and one lot for periodic inspection. No major changes in the manufacturing
process shall be made in the period during which the inspection lots are taken.
Samples shall be taken from the lots in accordance with IEC 60410. Normal inspection
shall be used, but when the sample size would give acceptance on zero defectives,
additional specimens shall be taken to meet the sample size requirements to give
acceptance on one defective.
2) The manufacturer shall produce test evidence to show conformance to the specification
requirements on the fixed sample size test schedule given in the sectional specification.
The specimens taken to form the sample shall be selected at random from current
production or as agreed with the National Supervising Inspectorate.
For the two procedures, the sample sizes and the number of permissible defectives shall be of
comparable order. The test conditions and requirements shall be the same.
3.5.4 Granting of qualification approval
Qualification approval shall be granted when the procedures in accordance with Clause 3 of
IEC QC 001002-3 have been completed satisfactorily.
3.5.5 Maintenance of qualification approval
Qualification approval shall be maintained by regular demonstration of compliance with the
requirements for quality conformance (see 3.5.6).
3.5.6 Quality conformance inspection
Blank detail specification(s) associated with the sectional specification shall prescribe the test

schedule for quality conformance inspection. This schedule shall also specify the grouping,
sampling and periodicity for the lot-by-lot and periodic inspection.
3.6 Capability approval procedures
3.6.1 Eligibility for capability approval
The manufacturer shall comply with 4.2.1 of IEC QC 001002-3.
3.6.2 Application for capability approval
The manufacturer shall comply with 4.2.4 of IEC QC 001002-3.

60939-1  IEC:2005(E) – 13 –
3.6.3 Description of capability

The description of the capability shall be made in a capability manual in accordance with

Clause 4 of IEC QC 001002-3 and the requirements of the relevant sectional specification.

The ONS shall treat the capability manual as a confidential document. The manufacturer may,

if he so wishes, disclose part or all of it to a third party.

3.6.4 Demonstration and verification of capability

The manufacturer shall demonstrate and verify the capability in accordance with Clause 4 of

IEC QC 001002-3 and the requirements of the relevant sectional specification.
3.6.5 Granting of capability approval
Capability approval shall be granted when the procedures in accordance with Clause 4 of
IEC QC 001002-3 have been completed satisfactorily.
3.6.6 Maintenance of capability approval
Capability approval shall be maintained by complying with the requirements in Clause 4 of
IEC QC 001002-3 and the requirements declared in the capability manual, following the
schedule of maintenance given in the relevant sectional specification.
3.6.7 Quality conformance inspection
The quality conformance test requirements are given in the detail specification and shall be
carried out in accordance with Clause 4 of IEC QC 001002-3.
The specimens taken to form the sample shall be selected at random from current production
or as agreed with the national supervising inspectorate.
3.7 Rework and repair work
3.7.1 Rework
Rework is the rectification of processing errors prior to the release of a filter.
It shall not be carried out if prohibited by the relevant sectional specification. The relevant
sectional specification shall state if there is a restriction on the number of occasions that
rework may take place on a specific component.

All rework shall be carried out prior to the formation of the inspection lot offered for inspection
to the requirements of the detail specification.
Such rework procedures shall be fully described in the relevant documentation produced by
the manufacturer and shall be carried out under the direct control of the chief inspector.
Subcontracting of rework is not permitted.
3.7.2 Repair
Repair is an activity to restore the good condition of an approved filter which has been
damaged or become defective after release.
Filters which have been repaired shall not be released under the IECQ-CECC system.

– 14 – 60939-1  IEC:2005(E)
3.8 Release for delivery
3.8.1 General
Filters shall be released for delivery according to IEC QC 001002-3 after the quality
conformance inspection prescribed in the detail specification has been carried out.

3.8.2 Release for delivery under qualification approval before the completion of
Group B tests
When the conditions of IEC 60410 for changing to reduced inspection have been satisfied for

all Group B tests, the manufacturer is permitted to release components before the completion

of such tests.
3.9 Certified test records
When certified test records are prescribed in the relevant specification and are requested by a
purchaser, the following information shall be given as a minimum:
a) attributes information (that is number of components tested and number of defective
components) for tests in the subgroups covered by periodic inspection without reference
to the parameter for which rejection was made;
b) variables information for the change in insertion loss and insulation resistance after the
endurance test, as required in the sectional specification.
NOTE For capability approval, the certified test records will refer only to tests carried out on capability qualifying
components.
3.10 Delayed delivery
Filters held for a period exceeding three years (unless otherwise specified in the sectional
specification), following the release of the lot shall, before delivery, be re-examined as
specified in the sectional specification.
The re-examination procedure adopted by the manufacturer's chief inspector shall be
approved by the ONS.
Once a lot has been satisfactorily re-inspected, its quality is re-assured for the specified
period.
3.11 Alternative test methods
The test and measurement methods given in the relevant specification are not necessarily the

only methods which can be used. However, the manufacturer shall satisfy the ONS that any
alternative methods which he may use will give results equivalent to those obtained by the
methods specified. In case of dispute, for referee and reference purposes, the specified
methods only shall be used.
3.12 Unchecked parameters
Only those parameters of a component which have been specified in a detail specification and
which are subject to testing can be assumed to be within the specified limits. It should not be
assumed that any parameter not specified will remain unchanged from one component to
another. Should for any reason it be necessary for one or more further parameters to be
controlled, then a new, more extensive specification should be used. The additional test
methods shall be fully described and appropriate limits, AQLs and inspection levels specified.

60939-1  IEC:2005(E) – 15 –
4 Test and measurement procedures

4.1 General
The sectional and/or blank detail specification shall contain tables showing the tests to be

made, which measurements are to be made before and after each test or subgroup of tests,

and the sequence in which they shall be carried out. The stages of each test shall be carried

out in the order written. The measuring conditions shall be the same for initial and final

measurements.
If national specifications within any Quality Assessment System include methods other than

those specified in the above documents, they shall be fully described.
4.2 Standard atmospheric conditions
4.2.1 Standard atmospheric conditions for testing
Unless otherwise specified, all tests and measurements shall be made under standard
atmospheric conditions for testing as given in 5.3 of IEC 60068-1.
– temperature: 15 °C to 35 °C;
– relative humidity: 45 % to 75 %;
– air pressure: 86 kPa to 106 kPa.
Before the measurements are made, the filter shall be stored at the measuring temperature
for a time sufficient to allow the entire filter to reach this temperature. The period prescribed
for recovery at the end of a test is normally sufficient for this purpose.
When measurements are made at a temperature other than the specified temperature, the
results shall, where necessary, be corrected to the specified temperature. The ambient
temperature during the measurements shall be stated in the test report. In the event of a
dispute, the measurements shall be repeated, using one of the referee temperatures (as given
in 4.2.3) and such other conditions as are prescribed in this Generic specification.
When tests are conducted in a sequence, the final measurements of one test may be taken as
the initial measurements for the succeeding test.
During measurements, the filter shall not be exposed to draughts, direct sunrays or other
influences likely to cause error.
4.2.2 Recovery conditions
Unless otherwise specified, recovery shall take place under the standard atmospheric
conditions for testing (see 4.2.1).
If recovery has to be made under closely controlled conditions, the controlled recovery
conditions of 5.4.1 of IEC 60068-1 shall be used.
Unless otherwise specified in the relevant sectional or detail specification, a duration of 1 h to
2 h shall be used.
4.2.3 Referee conditions
For referee purposes, one of the standard atmospheric conditions for referee tests taken from
5.2 of IEC 60068-1, as given in Table 1, shall be chosen.

– 16 – 60939-1  IEC:2005(E)
Table 1 – Standard atmospheric conditions

Temperature Relative humidity Air pressure

°C % kPa
20 ± 1 63 to 67 86 to 106
23 ± 1 48 to 52 86 to 106
25 ± 1 48 to 52 86 to 106
27 ± 1 63 to 67 86 to 106
4.2.4 Reference conditions
For reference purposes, the standard atmospheric conditions for reference given in 5.1 of
IEC 60068-1 apply:
– temperature: 20 °C;
– air pressure: 101,3 kPa.
4.3 Drying
Unless otherwise specified in the relevant specification, the filter shall be conditioned for
(96 ± 4) h by heating in a circulating air oven at a temperature of (55 ± 2) °C and a relative
humidity not exceeding 20 %.
The filter shall then be allowed to cool in a desiccator using a suitable desiccant, such as
activated alumina or silica gel, and shall be kept therein from the time of removal from the
oven to the beginning of the specified tests.
4.4 Visual examination and check of dimensions
4.4.1 Visual examination
The condition, workmanship and finish shall be satisfactory, as checked by visual examination
(see 2.2.15).
Marking shall be legible, as checked by visual examination. It shall conform to the
requirements of the detail specification.
4.4.2 Dimensions (gauging)
The dimensions indicated in the detail specification as being suitable for gauging shall be
checked, and shall comply with the values prescribed in the detail specification.
When applicable, measurements shall be made in accordance with IEC 60294.
4.4.3 Dimensions (detail)
All dimensions prescribed in the detail specification shall be checked and shall comply with
the values prescribed.
4.4.4 Creepage distances and clearances
For those filters for which safety tests are appropriate, creepage distances and clearances on
the outside of the filter between live parts of different polarity or between live parts and a
metal case shall be not less than the appropriate values prescribed in the relevant
specification.
60939-1  IEC:2005(E) – 17 –
4.5 Insulation resistance
For filters fitted with a discharge resistor, this measurement can only be made with the

discharge resistor disconnected. If the discharge resistor cannot be disconnected without the

filter being destroyed, the test shall be omitted for lot-by-lot tests; for qualification approval

and periodic tests, where the discharge resistor cannot be disconnected without the filter

being destroyed, the sample shall consist of filters specially made without discharge resistors.

4.5.1 Measuring voltage
Before the measurement is made, the filters shall be fully discharged. Unless otherwise

specified in the relevant specification, the insulation resistance shall be measured, at the d.c.
voltage specified in Table 2.
Table 2 – DC voltage for insulation resistance
Voltage rating of the filter Measuring voltage
U or U <  10 V U or U ± 10 %
R C C R
a)
(10 ± 1) V
10 V ≤ U or U < 100 V
R C
(100 ± 15) V
100 V ≤ U or U < 500 V
R C
(500 ± 50) V
500 V ≤ U or U
R C
a)
When it can be demonstrated that the voltage has no influence on
the measuring result, or that a known relationship exists,
measurement can be performed at voltages up to the rated or
category voltage (10 V shall be used in
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