Components for low-voltage surge protection - Part 331: Performance requirements and test methods for metal oxide varistors (MOV)

IEC 61643-331:2020 is available as IEC 61643-331:2020 RLV which contains the International Standard and its Redline version, showing all changes of the technical content compared to the previous edition.
IEC 61643-331:2020 is a test specification for metal oxide varistors (MOV), which are used for applications up to 1 000 V AC or 1 500 V DC in power lines, or telecommunication, or signalling circuits. They are designed to protect apparatus or personnel, or both, from high transient voltages. This document applies to MOVs having two electrodes and hybrid surge protection components. This document also does not apply to mountings and their effect on the MOV’s characteristics. Characteristics given apply solely to the MOV mounted only in the ways described for the tests. This third edition cancels and replaces the second edition published in 2017. This edition constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition:
- a Varistor MCOV rating assurance test;
- an energy rating test (2ms);
- revised Dielectric strength and insulation resistance tests.

Composants pour parafoudres basse tension - Partie 331: Exigences de performance et méthodes d'essai pour les varistances à oxyde métallique (MOV)

IEC 61643-331:2020 est disponible sous forme de IEC 61643-331:2020 RLV qui contient la Norme internationale et sa version Redline, illustrant les modifications du contenu technique depuis l'édition précédente.
IEC 61643-331:2020 est une spécification d'essai pour les varistances à oxyde métallique (MOV, Metal Oxide Varistor) utilisées dans des applications jusqu'à 1 000 V en courant alternatif ou 1 500 V en courant continu sur les lignes électriques ou de télécommunication, ou dans les circuits de signalisation. Elles sont conçues pour protéger l'appareillage et/ou le personnel contre les hautes tensions transitoires. Le présent document s'applique aux MOV comportant deux électrodes et des composants pour parafoudres hybrides. Le présent document ne s'applique pas aux montages et à leurs effets sur les caractéristiques des MOV. Les caractéristiques indiquées s'appliquent exclusivement aux MOV montées uniquement dans le sens décrit pour les essais. Cette troisième édition annule et remplace la deuxième édition parue en 2017. Cette édition constitue une révision technique. Cette édition inclut les modifications techniques majeures suivantes par rapport à l'édition précédente:
- un essai d'assurance des caractéristiques MCOV assignées de la varistance a été ajouté;
- un essai des caractéristiques assignées d'énergie (2 ms) a été ajouté;
- les essais de rigidité diélectrique et de résistance d'isolement ont été revus.

General Information

Status
Published
Publication Date
18-Mar-2020
Current Stage
PPUB - Publication issued
Completion Date
19-Mar-2020
Ref Project

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IEC 61643-331
Edition 3.0 2020-03
INTERNATIONAL
STANDARD
colour
inside
Components for low-voltage surge protection –
Part 331: Performance requirements and test methods for metal oxide varistors
(MOV)
IEC 61643-331:2020-03(en)
---------------------- Page: 1 ----------------------
THIS PUBLICATION IS COPYRIGHT PROTECTED
Copyright © 2020 IEC, Geneva, Switzerland

All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form

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---------------------- Page: 2 ----------------------
IEC 61643-331
Edition 3.0 2020-03
INTERNATIONAL
STANDARD
colour
inside
Components for low-voltage surge protection –
Part 331: Performance requirements and test methods for metal oxide varistors
(MOV)
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 31.040.20 ISBN 978-2-8322-7905-2

Warning! Make sure that you obtained this publication from an authorized distributor.

® Registered trademark of the International Electrotechnical Commission
---------------------- Page: 3 ----------------------
– 2 – IEC 61643-331:2020 © IEC 2020
CONTENTS

FOREWORD ........................................................................................................................... 5

1 Scope .............................................................................................................................. 7

2 Normative references ...................................................................................................... 7

3 Terms, definitions, symbols and abbreviated terms .......................................................... 8

3.1 Terms and definitions .............................................................................................. 8

3.1.1 Ratings ............................................................................................................ 8

3.1.2 Characteristics................................................................................................. 9

3.2 Symbols and abbreviated terms used in this document ......................................... 11

3.2.1 Symbols ........................................................................................................ 11

3.2.2 Abbreviated terms ......................................................................................... 11

4 Service conditions ......................................................................................................... 12

4.1 Operating and storage temperature ranges ........................................................... 12

4.2 Altitude or atmospheric pressure range ................................................................. 12

4.3 Relative Humidity .................................................................................................. 12

5 Mechanical requirements and materials ......................................................................... 12

5.1 Robustness of terminations ................................................................................... 12

5.2 Solderability .......................................................................................................... 12

5.3 Marking ................................................................................................................. 12

6 General ......................................................................................................................... 13

6.1 Failure rates ......................................................................................................... 13

6.2 Test standard atmospheric conditions ................................................................... 13

7 Electrical requirements .................................................................................................. 13

7.1 Varistor voltage (V ) ............................................................................................. 13

7.2 Maximum AC (DC) continuous voltage (V / V ) ....................................... 13

M(AC) M(DC)

7.3 Standby current (I ) .............................................................................................. 13

7.4 Capacitance (C ) .................................................................................................. 13

7.5 Clamping voltage (V ) ........................................................................................... 13

7.6 Electrostatic discharge (ESD) (for SMD type MOV only)........................................ 15

7.7 Rated impulse energy ........................................................................................... 15

7.8 Nominal discharge current (I ) .............................................................................. 15

7.9 Endurance ............................................................................................................ 15

7.10 Limited current temporary overvoltage .................................................................. 15

8 Standard design test criteria .......................................................................................... 16

8.1 General ................................................................................................................. 16

8.2 Ratings ................................................................................................................. 16

8.2.1 Single-impulse maximum current (I ) ........................................................... 16

8.2.2 Next impulse .................................................................................................. 16

8.2.3 Maximum Continuous voltage (V ) ................................................................ 17

8.3 Electrical Characteristics ...................................................................................... 17

8.3.1 Clamping voltage (V ) ................................................................................... 17

8.3.2 Standby current (I ) ...................................................................................... 17

8.3.3 Varistor voltage (V ) ...................................................................................... 17

8.3.4 Capacitance (C ) ........................................................................................... 18

8.3.5 Rated energy ................................................................................................. 18

8.4 Varistor Rating Assurance Testing ........................................................................ 18

---------------------- Page: 4 ----------------------
IEC 61643-331:2020 © IEC 2020 – 3 –

8.5 ESD test ............................................................................................................... 19

9 Nominal discharge current and limited current temporary overvoltage............................ 19

9.1 Thermally protected varistors – Sequence of tests ................................................ 19

9.2 Temperature and humidity cycle conditioning ........................................................ 19

9.3 Nominal discharge current (I ) test description ..................................................... 20

9.3.1 General ......................................................................................................... 20

9.3.2 Pass/fail criteria ............................................................................................. 22

9.4 Limited current temporary overvoltage test description and procedure for

thermally protected varistors ................................................................................. 22

9.4.1 General ......................................................................................................... 22

9.4.2 Sample preparation ....................................................................................... 23

9.4.3 Test conditions .............................................................................................. 23

9.4.4 Pass/fail criteria ............................................................................................. 23

9.5 Dielectric testing ................................................................................................... 24

9.5.1 Test conditions for thermally protected MOV .................................................. 24

9.5.2 Setup from foil to leads .................................................................................. 25

9.5.3 Pass criteria .................................................................................................. 25

9.6 Insulation Resistance ............................................................................................ 25

Annex A (informative) MOV testing according to the IEC 61643-11:2011 Surge

protective devices for the Class I, II and III ........................................................................... 26

A.1 General ................................................................................................................. 26

A.2 MOV selection ...................................................................................................... 26

A.3 Cross reference list of abbreviations, descriptions and definitions ......................... 26

A.4 Operating duty test ............................................................................................... 27

A.4.1 General ......................................................................................................... 27

A.4.2 Class I and II operating duty tests (8.4.4.3) ................................................... 32

A.4.3 Additional duty test for test class I ................................................................. 33

A.4.4 Class III operating duty tests ......................................................................... 33

A.4.5 Pass criteria for all operating duty tests and for the additional duty test

for test class I ................................................................................................ 34

A.4.6 Preferred parameters of impulse discharge current I used for Class I
imp

additional duty tests ....................................................................................... 34

A.4.7 Preferred values of impulse discharge current I used for Class I and

Class II residual voltage and operating duty tests .......................................... 35

A.4.8 Preferred values of combination generator waveshape used for Class III

tests .............................................................................................................. 35

Annex B (informative) IEC 61051 Varistors for use in electronic equipment ......................... 38

Annex C (normative) Accelerated Endurance screening test ................................................ 39

C.1 Accelerated endurance screening test .................................................................. 39

C.2 Preparation of sample ........................................................................................... 39

C.3 Test conditions ..................................................................................................... 39

C.4 Refer to test circuit diagram as shown in Figure C.1. ............................................ 39

C.5 Pass criteria .......................................................................................................... 40

Annex D (informative) Proposed test method of MTTF – Mean time to failure (MTTF) .......... 41

D.1 Sampling plans ..................................................................................................... 41

D.2 Total test hours ..................................................................................................... 41

D.3 Samples................................................................................................................ 41

D.4 Test set-up ........................................................................................................... 42

D.5 Intermediate measurements .................................................................................. 42

D.6 Failure criteria ....................................................................................................... 42

---------------------- Page: 5 ----------------------
– 4 – IEC 61643-331:2020 © IEC 2020

D.7 Acceptance criteria ............................................................................................... 42

Figure 1 – V-I characteristic of an MOV ................................................................................ 10

Figure 2 – Symbol for MOV ................................................................................................... 11

Figure 3 – Symbol for thermally protected MOV .................................................................... 11

Figure 4 – Test circuit for single-impulse maximum current ................................................... 16

Figure 5 – Test circuit for measuring standby current ............................................................ 17

Figure 6 – Test circuit for measuring varistor voltage (V ) .................................................... 18

Figure 7 – Varistor rating assurance test setup ..................................................................... 19

Figure 8 – Nominal discharge current test flowchart .............................................................. 21

Figure 9 – Sequence of the I Test ....................................................................................... 22

Figure 10 – Temporary overvoltage limited current test procedure flowchart ......................... 24

Figure A.1 – Flow chart of the operating duty test ................................................................. 28

Figure A.2 – Test set-up for operating duty test .................................................................... 29

Figure A.3 – Flow chart of testing to determine the measured limiting voltage ....................... 31

Figure A.4 – Operating duty test timing diagram for test classes I and II ............................... 32

Figure A.5 – Additional duty test timing diagram for test class I ............................................ 33

Figure A.6 – Operating duty test timing diagram for test class III ........................................... 34

Figure C.1 – Circuit of accelerated ageing test ...................................................................... 39

Figure D.1 – Test Circuit of MTTF ......................................................................................... 42

Table 1 – Typical Voltage ratings for disc types .................................................................... 14

Table 2 – Typical Voltage Ratings for SMD types .................................................................. 15

Table 3 – Test voltages for dielectric strength Between Test voltage .................................... 25

Table A.1 – Abbreviations, descriptions and definitions ......................................................... 27

Table A.2 – Preferred parameters for class I test .................................................................. 34

Table A.3 – Preferred values for class I and class II tests ..................................................... 35

Table A.4 – Preferred values for class III tests ...................................................................... 36

Table C.1 – Current in V measurement ................................................................................ 39

Table D.1 – Sampling plans .................................................................................................. 41

---------------------- Page: 6 ----------------------
IEC 61643-331:2020 © IEC 2020 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
COMPONENTS FOR LOW-VOLTAGE SURGE PROTECTION –
Part 331: Performance requirements and test methods
for metal oxide varistors (MOV)
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

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4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications

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5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity

assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any

services carried out by independent certification bodies.

6) All users should ensure that they have the latest edition of this publication.

7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and

members of its technical committees and IEC National Committees for any personal injury, property damage or

other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and

expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC

Publications.

8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is

indispensable for the correct application of this publication.

9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of

patent rights. IEC shall not be held responsible for identifying any or all such patent rights.

International Standard IEC 61643-331 has been prepared by subcommittee 37B: Components

for low-voltage surge protection, of IEC technical committee 37: Surge arresters.

This third edition cancels and replaces the second edition published in 2017. This edition

constitutes a technical revision.

This edition includes the following significant technical changes with respect to the previous

edition:
a) a Varistor MCOV rating assurance test;
b) an energy rating test (2ms);
c) revised Dielectric strength and insulation resistance tests.
---------------------- Page: 7 ----------------------
– 6 – IEC 61643-331:2020 © IEC 2020
The text of this International Standard is based on the following documents:
FDIS Report on voting
37B/211/FDIS 37B/214/RVD

Full information on the voting for the approval of this International Standard can be found in

the report on voting indicated in the above table.

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

A list of all parts of IEC 61643 series, under the general title Components for low-voltage

surge protective devices, 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.

IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates

that it contains colours which are considered to be useful for the correct

understanding of its contents. Users should therefore print this document using a

colour printer.
---------------------- Page: 8 ----------------------
IEC 61643-331:2020 © IEC 2020 – 7 –
COMPONENTS FOR LOW-VOLTAGE SURGE PROTECTION –
Part 331: Performance requirements and test methods
for metal oxide varistors (MOV)
1 Scope

This part of IEC 61643 is a test specification for metal oxide varistors (MOV), which are used

for applications up to 1 000 V AC or 1 500 V DC in power lines, or telecommunication, or

signalling circuits. They are designed to protect apparatus or personnel, or both, from high

transient voltages.
This document applies to MOVs having two electrodes and hybrid surge protection

components. This document also does not apply to mountings and their effect on the MOV’s

characteristics. Characteristics given apply solely to the MOV mounted only in the ways

described for the tests.
2 Normative references

The following documents are referred to in the text in such a way that some or all of their

content constitutes requirements of this document. For dated references, only the edition

cited applies. For undated references, the latest edition of the referenced document (including

any amendments) applies.
IEC 60068-1:2013, Environmental testing – Part 1: General and guidance

IEC 60068-2-6:2007, Environmental testing – Part 2-6: Tests – Test Fc: Vibration (sinusoidal)

IEC 60068-2-14:2009, Environmental testing – Part 2-14: Tests – Test N: Change of

temperature

IEC 60068-2-20:2008, Environmental testing – Part 2-20: Tests – Test T: Test methods for

solderability and resistance to soldering heat of devices with leads

IEC 60068-2-21:2006, Environmental testing – Part 2-21: Tests – Test U: Robustness of

terminations and integral mounting devices

IEC 60068-2-27:2008, Environmental testing – Part 2-27: Tests – Test Ea and guidance:

Shock

IEC 60068-2-52:2017 Environmental testing – Part 2-52: Tests – Test Kb: Salt mist, cyclic

(sodium chloride solution)

IEC 61643-11:2011, Low-voltage surge protective devices – Part 11: Surge protective devices

connected to low-voltage power systems – Requirements and test methods
IEC 61000-4-2:2008, Electromagnetic compatibility (EMC) – Part 4-2: Testing and
measurement techniques – Electrostatic discharge immunity test
---------------------- Page: 9 ----------------------
– 8 – IEC 61643-331:2020 © IEC 2020
3 Terms, definitions, symbols and abbreviated terms
For the purposes of this document, the following terms and definitions 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
3.1 Terms and definitions
3.1.1 Ratings
3.1.1.1
absolute maximum ratings

limiting values of operating and environmental conditions applicable to a component, device,

equipment or machine as defined by its published specification data, which should not be

exceeded under the worst possible conditions

Note 1 to entry: A limiting condition may be either a maximum or a minimum or both.

[SOURCE: IEC 62240-1:2013, 3.1.1, modified ("any semiconductor device of a specific type"

replaced by "a component, device, equipment or machine", addition of Note 1 to entry)]

3.1.1.2
single-impulse [transient] maximum current

rated maximum value of current which may be applied for a single impulse of specified

waveform

Note 1 to entry: For power distribution SPDs, IEC 61643-11, Maximum Discharge Current I is used.

MAX
3.1.1.3
nominal discharge current
crest value of the current through the MOV having a current waveshape of 8/20
3.1.1.4
impulse life characteristic

graphical representation between impulse current peak (I), equivalent rectangular pulse width

(T), and impulse numbers (n) which the MOV can withstand

Note 1 to entry: Unless otherwise specified, the range of T shall be 20 µs to 10 ms, the range of n shall be 10 ,

5 4 3 2 1 0
10 ,10 , 10 , 10 , 10 and 10 .
3.1.1.5
temperature derating curve
graphical representation of parameter derating against temperature

Note 1 to entry: Typical parameters are rated voltage, impulse current, energy and average power dissipation.

3.1.1.6
single-pulse [transient] maximum energy

rated maximum value which may be absorbed for a single pulse of a specified waveform

Note 1 to entry: Unless otherwise specified, 2 ms rectangular pulse is used (IEC 60060).

---------------------- Page: 10 ----------------------
IEC 61643-331:2020 © IEC 2020 – 9 –
3.1.1.7
maximum continuous voltage
voltage that may be applied continuously at a specified temperature
Note 1 to entry: May also be called U or MCOV.
Note 2 to entry: See Figure 1.
3.1.1.8
maximum continuous AC voltage
M(AC)

value of RMS power frequency voltage (less than 5 % total harmonic distortion) that may be

applied continuously at a specified temperature
3.1.1.9
maximum continuous DC voltage
M(DC)
DC voltage that may be applied continuously at a specified temperature
3.1.1.10
mean time to failure
MTTF

basic measure of reliability for non-repairable items, the total number of life units of an item

divided by the total number of failures within that population ,during a particular measurement

interval under stated conditions
3.1.2 Characteristics
3.1.2.1
characteristic
inherent and measurable properties of an MOV
3.1.2.2
standby current
current passing through MOV at maximum continuous voltage V

Note 1 to entry: The current passing through the MOV at less than V is called leakage current.

3.1.2.3
varistor voltage

voltage across the MOV measured at a specified current (typically 1 mA) for a specific

duration
3.1.2.4
varistor test current
test current (typically 1 mA) to determine the varistor voltage V
Note 1 to entry: See Figure 1.
3.1.2.5
clamping voltage

peak voltage across the MOV measured under conditions of a specified peak pulse current

(I ) and specified waveform
Note 1 to entry: See Figure 1.
---------------------- Page: 11 ----------------------
– 10 – IEC 61643-331:2020 © IEC 2020

Note 2 to entry: Unless otherwise specified, a typical value of this parameter is measured with a pulsed current

8/20 waveform.

Note 3 to entry: Clamping voltage, V , is referred to as measured limiting voltage in IEC 61643-11.

Figure 1 – V-I characteristic of an MOV
3.1.2.6
capacitance
capacitance across the MOV measured at a specified frequency, voltage and tim
...

IEC 61643-331
Edition 3.0 2020-03
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Components for low-voltage surge protection –
Part 331: Performance requirements and test methods for metal oxide varistors
(MOV)
Composants pour parafoudres basse tension –
Partie 331: Exigences de performance et méthodes d'essai pour les varistances
à oxyde métallique (MOV)
IEC 61643-331:2020-03(en-fr)
---------------------- Page: 1 ----------------------
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About the IEC

The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes

International Standards for all electrical, electronic and related technologies.
About IEC publications

The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the

latest edition, a corrigendum or an amendment might have been published.

IEC publications search - webstore.iec.ch/advsearchform Electropedia - www.electropedia.org

The advanced search enables to find IEC publications by a The world's leading online dictionary on electrotechnology,

variety of criteria (reference number, text, technical containing more than 22 000 terminological entries in English

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and withdrawn publications. Also known as the International Electrotechnical Vocabulary

(IEV) online.
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Stay up to date on all new IEC publications. Just Published IEC Glossary - std.iec.ch/glossary

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publications issued since 2002. Some entries have been

IEC Customer Service Centre - webstore.iec.ch/csc collected from earlier publications of IEC TC 37, 77, 86 and

If you wish to give us your feedback on this publication or need CISPR.
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Centre: sales@iec.ch.
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IEC 61643-331
Edition 3.0 2020-03
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Components for low-voltage surge protection –
Part 331: Performance requirements and test methods for metal oxide varistors
(MOV)
Composants pour parafoudres basse tension –
Partie 331: Exigences de performance et méthodes d'essai pour les varistances
à oxyde métallique (MOV)
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 31.040.20 ISBN 978-2-8322-8558-9

Warning! Make sure that you obtained this publication from an authorized distributor.

Attention! Veuillez vous assurer que vous avez obtenu cette publication via un distributeur agréé.

® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale
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– 2 – IEC 61643-331:2020 © IEC 2020
CONTENTS

FOREWORD ........................................................................................................................... 5

1 Scope .............................................................................................................................. 7

2 Normative references ...................................................................................................... 7

3 Terms, definitions, symbols and abbreviated terms .......................................................... 8

3.1 Terms and definitions .............................................................................................. 8

3.1.1 Ratings ............................................................................................................ 8

3.1.2 Characteristics................................................................................................. 9

3.2 Symbols and abbreviated terms used in this document ......................................... 11

3.2.1 Symbols ........................................................................................................ 11

3.2.2 Abbreviated terms ......................................................................................... 11

4 Service conditions ......................................................................................................... 12

4.1 Operating and storage temperature ranges ........................................................... 12

4.2 Altitude or atmospheric pressure range ................................................................. 12

4.3 Relative Humidity .................................................................................................. 12

5 Mechanical requirements and materials ......................................................................... 12

5.1 Robustness of terminations ................................................................................... 12

5.2 Solderability .......................................................................................................... 12

5.3 Marking ................................................................................................................. 12

6 General ......................................................................................................................... 13

6.1 Failure rates ......................................................................................................... 13

6.2 Test standard atmospheric conditions ................................................................... 13

7 Electrical requirements .................................................................................................. 13

7.1 Varistor voltage (V ) ............................................................................................. 13

7.2 Maximum AC (DC) continuous voltage (V / V ) ....................................... 13

M(AC) M(DC)

7.3 Standby current (I ) .............................................................................................. 13

7.4 Capacitance (C ) .................................................................................................. 13

7.5 Clamping voltage (V ) ........................................................................................... 13

7.6 Electrostatic discharge (ESD) (for SMD type MOV only)........................................ 15

7.7 Rated impulse energy ........................................................................................... 15

7.8 Nominal discharge current (I ) .............................................................................. 15

7.9 Endurance ............................................................................................................ 15

7.10 Limited current temporary overvoltage .................................................................. 15

8 Standard design test criteria .......................................................................................... 16

8.1 General ................................................................................................................. 16

8.2 Ratings ................................................................................................................. 16

8.2.1 Single-impulse maximum current (I ) ........................................................... 16

8.2.2 Next impulse .................................................................................................. 16

8.2.3 Maximum Continuous voltage (V ) ................................................................ 17

8.3 Electrical Characteristics ...................................................................................... 17

8.3.1 Clamping voltage (V ) ................................................................................... 17

8.3.2 Standby current (I ) ...................................................................................... 17

8.3.3 Varistor voltage (V ) ...................................................................................... 17

8.3.4 Capacitance (C ) ........................................................................................... 18

8.3.5 Rated energy ................................................................................................. 18

8.4 Varistor Rating Assurance Testing ........................................................................ 18

8.5 ESD test ............................................................................................................... 19

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IEC 61643-331:2020 © IEC 2020 – 3 –

9 Nominal discharge current and limited current temporary overvoltage............................ 19

9.1 Thermally protected varistors – Sequence of tests ................................................ 19

9.2 Temperature and humidity cycle conditioning ........................................................ 19

9.3 Nominal discharge current (I ) test description ..................................................... 20

9.3.1 General ......................................................................................................... 20

9.3.2 Pass/fail criteria ............................................................................................. 22

9.4 Limited current temporary overvoltage test description and procedure for

thermally protected varistors ................................................................................. 22

9.4.1 General ......................................................................................................... 22

9.4.2 Sample preparation ....................................................................................... 23

9.4.3 Test conditions .............................................................................................. 23

9.4.4 Pass/fail criteria ............................................................................................. 23

9.5 Dielectric testing ................................................................................................... 24

9.5.1 Test conditions for thermally protected MOV .................................................. 24

9.5.2 Setup from foil to leads .................................................................................. 25

9.5.3 Pass criteria .................................................................................................. 25

9.6 Insulation Resistance ............................................................................................ 25

Annex A (informative) MOV testing according to the IEC 61643-11:2011 Surge

protective devices for the Class I, II and III ........................................................................... 26

A.1 General ................................................................................................................. 26

A.2 MOV selection ...................................................................................................... 26

A.3 Cross reference list of abbreviations, descriptions and definitions ......................... 26

A.4 Operating duty test ............................................................................................... 27

A.4.1 General ......................................................................................................... 27

A.4.2 Class I and II operating duty tests (8.4.4.3) ................................................... 32

A.4.3 Additional duty test for test class I ................................................................. 33

A.4.4 Class III operating duty tests ......................................................................... 33

A.4.5 Pass criteria for all operating duty tests and for the additional duty test

for test class I ................................................................................................ 34

A.4.6 Preferred parameters of impulse discharge current I used for Class I
imp

additional duty tests ....................................................................................... 34

A.4.7 Preferred values of impulse discharge current I used for Class I and

Class II residual voltage and operating duty tests .......................................... 35

A.4.8 Preferred values of combination generator waveshape used for Class III

tests .............................................................................................................. 36

Annex B (informative) IEC 61051 Varistors for use in electronic equipment ......................... 38

Annex C (normative) Accelerated Endurance screening test ................................................ 39

C.1 Accelerated endurance screening test .................................................................. 39

C.2 Preparation of sample ........................................................................................... 39

C.3 Test conditions ..................................................................................................... 39

C.4 Refer to test circuit diagram as shown in Figure C.1. ............................................ 39

C.5 Pass criteria .......................................................................................................... 40

Annex D (informative) Proposed test method of MTTF – Mean time to failure (MTTF) .......... 41

D.1 Sampling plans ..................................................................................................... 41

D.2 Total test hours ..................................................................................................... 41

D.3 Samples................................................................................................................ 41

D.4 Test set-up ........................................................................................................... 42

D.5 Intermediate measurements .................................................................................. 42

D.6 Failure criteria ....................................................................................................... 42

D.7 Acceptance criteria ............................................................................................... 42

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– 4 – IEC 61643-331:2020 © IEC 2020

Figure 1 – V-I characteristic of an MOV ................................................................................ 10

Figure 2 – Symbol for MOV ................................................................................................... 11

Figure 3 – Symbol for thermally protected MOV .................................................................... 11

Figure 4 – Test circuit for single-impulse maximum current ................................................... 16

Figure 5 – Test circuit for measuring standby current ............................................................ 17

Figure 6 – Test circuit for measuring varistor voltage (V ) ..................................................... 18

Figure 7 – Varistor rating assurance test setup ..................................................................... 19

Figure 8 – Nominal discharge current test flowchart .............................................................. 21

Figure 9 – Sequence of the I Test ....................................................................................... 22

Figure 10 – Temporary overvoltage limited current test procedure flowchart ......................... 24

Figure A.1 – Flow chart of the operating duty test ................................................................. 28

Figure A.2 – Test set-up for operating duty test .................................................................... 29

Figure A.3 – Flow chart of testing to determine the measured limiting voltage ....................... 31

Figure A.4 – Operating duty test timing diagram for test classes I and II ............................... 32

Figure A.5 – Additional duty test timing diagram for test class I ............................................ 33

Figure A.6 – Operating duty test timing diagram for test class III ........................................... 34

Figure C.1 – Circuit of accelerated ageing test ...................................................................... 39

Figure D.1 – Test Circuit of MTTF ......................................................................................... 42

Table 1 – Typical Voltage ratings for disc types .................................................................... 14

Table 2 – Typical Voltage Ratings for SMD types .................................................................. 15

Table 3 – Test voltages for dielectric strength Between Test voltage .................................... 25

Table A.1 – Abbreviations, descriptions and definitions ......................................................... 27

Table A.2 – Preferred parameters for class I test .................................................................. 34

Table A.3 – Preferred values for class I and class II tests ..................................................... 35

Table A.4 – Preferred values for class III tests ...................................................................... 36

Table C.1 – Current in V measurement ................................................................................ 39

Table D.1 – Sampling plans .................................................................................................. 41

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IEC 61643-331:2020 © IEC 2020 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
COMPONENTS FOR LOW-VOLTAGE SURGE PROTECTION –
Part 331: Performance requirements and test methods
for metal oxide varistors (MOV)
FOREWORD

1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising

all national electrotechnical committees (IEC National Committees). The object of IEC is to promote

international co-operation on all questions concerning standardization in the electrical and electronic fields. To

this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,

Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC

Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested

in the subject dealt with may participate in this preparatory work. International, governmental and non-

governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely

with the International Organization for Standardization (ISO) in accordance with conditions determined by

agreement between the two organizations.

2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international

consensus of opinion on the relevant subjects since each technical committee has representation from all

interested IEC National Committees.

3) IEC Publications have the form of recommendations for international use and are accepted by IEC National

Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC

Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any

misinterpretation by any end user.

4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications

transparently to the maximum extent possible in their national and regional publications. Any divergence

between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in

the latter.

5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity

assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any

services carried out by independent certification bodies.

6) All users should ensure that they have the latest edition of this publication.

7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and

members of its technical committees and IEC National Committees for any personal injury, property damage or

other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and

expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC

Publications.

8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is

indispensable for the correct application of this publication.

9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of

patent rights. IEC shall not be held responsible for identifying any or all such patent rights.

International Standard IEC 61643-331 has been prepared by subcommittee 37B: Components

for low-voltage surge protection, of IEC technical committee 37: Surge arresters.

This third edition cancels and replaces the second edition published in 2017. This edition

constitutes a technical revision.

This edition includes the following significant technical changes with respect to the previous

edition:
a) a Varistor MCOV rating assurance test;
b) an energy rating test (2ms);
c) revised Dielectric strength and insulation resistance tests.
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– 6 – IEC 61643-331:2020 © IEC 2020
The text of this International Standard is based on the following documents:
FDIS Report on voting
37B/211/FDIS 37B/214/RVD

Full information on the voting for the approval of this International Standard can be found in

the report on voting indicated in the above table.

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

A list of all parts of IEC 61643 series, under the general title Components for low-voltage

surge protective devices, 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.

IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates

that it contains colours which are considered to be useful for the correct

understanding of its contents. Users should therefore print this document using a

colour printer.
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IEC 61643-331:2020 © IEC 2020 – 7 –
COMPONENTS FOR LOW-VOLTAGE SURGE PROTECTION –
Part 331: Performance requirements and test methods
for metal oxide varistors (MOV)
1 Scope

This part of IEC 61643 is a test specification for metal oxide varistors (MOV), which are used

for applications up to 1 000 V AC or 1 500 V DC in power lines, or telecommunication, or

signalling circuits. They are designed to protect apparatus or personnel, or both, from high

transient voltages.
This document applies to MOVs having two electrodes and hybrid surge protection

components. This document also does not apply to mountings and their effect on the MOV’s

characteristics. Characteristics given apply solely to the MOV mounted only in the ways

described for the tests.
2 Normative references

The following documents are referred to in the text in such a way that some or all of their

content constitutes requirements of this document. For dated references, only the edition

cited applies. For undated references, the latest edition of the referenced document (including

any amendments) applies.
IEC 60068-1:2013, Environmental testing – Part 1: General and guidance

IEC 60068-2-6:2007, Environmental testing – Part 2-6: Tests – Test Fc: Vibration (sinusoidal)

IEC 60068-2-14:2009, Environmental testing – Part 2-14: Tests – Test N: Change of

temperature

IEC 60068-2-20:2008, Environmental testing – Part 2-20: Tests – Test T: Test methods for

solderability and resistance to soldering heat of devices with leads

IEC 60068-2-21:2006, Environmental testing – Part 2-21: Tests – Test U: Robustness of

terminations and integral mounting devices

IEC 60068-2-27:2008, Environmental testing – Part 2-27: Tests – Test Ea and guidance:

Shock

IEC 60068-2-52:2017 Environmental testing – Part 2-52: Tests – Test Kb: Salt mist, cyclic

(sodium chloride solution)

IEC 61643-11:2011, Low-voltage surge protective devices – Part 11: Surge protective devices

connected to low-voltage power systems – Requirements and test methods
IEC 61000-4-2:2008, Electromagnetic compatibility (EMC) – Part 4-2: Testing and
measurement techniques – Electrostatic discharge immunity test
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– 8 – IEC 61643-331:2020 © IEC 2020
3 Terms, definitions, symbols and abbreviated terms
For the purposes of this document, the following terms and definitions 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
3.1 Terms and definitions
3.1.1 Ratings
3.1.1.1
absolute maximum ratings

limiting values of operating and environmental conditions applicable to a component, device,

equipment or machine as defined by its published specification data, which should not be

exceeded under the worst possible conditions

Note 1 to entry: A limiting condition may be either a maximum or a minimum or both.

[SOURCE: IEC 62240-1:2013, 3.1.1, modified ("any semiconductor device of a specific type"

replaced by "a component, device, equipment or machine", addition of Note 1 to entry)]

3.1.1.2
single-impulse [transient] maximum current

rated maximum value of current which may be applied for a single impulse of specified

waveform

Note 1 to entry: For power distribution SPDs, IEC 61643-11, Maximum Discharge Current I is used.

MAX
3.1.1.3
nominal discharge current
crest value of the current through the MOV having a current waveshape of 8/20
...

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