EN IEC 61643-331:2018

SLOVENSKI STANDARD
01-maj-2018
1DGRPHãþD
SIST EN 61643-331:2003
6HVWDYQLGHOL]DQL]NRQDSHWRVWQHQDSUDYH]D]DãþLWRSUHGSUHQDSHWRVWQLPLXGDUL
GHO=DKWHYH]DODVWQRVWLLQSUHVNXVQHPHWRGH]DNRYLQVNRRNVLGQHYDULVWRUMH
Components for low-voltage surge protection - Part 331: Performance requirements and
test methods for metal oxide varistors (MOV)
Ta slovenski standard je istoveten z: EN IEC 61643-331:2018
ICS:
29.120.50 9DURYDONHLQGUXJD Fuses and other overcurrent
PHGWRNRYQD]DãþLWD protection devices
31.040.20 Potenciometri, spremenljivi Potentiometers, variable
upori resistors
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD EN IEC 61643-331

NORME EUROPÉENNE
EUROPÄISCHE NORM
March 2018
ICS 31.040 Supersedes EN 61643-331:2003
English Version
Components for low-voltage surge protective devices - Part 331:
Performance requirements and test methods for metal oxide
varistors (MOV)
(IEC 61643-331:2017)
Composants pour protection par parafoudres basse tension Bauelemente für Überspannungsschutzgeräte für
- Partie 331: Exigences de performance et méthodes Niederspannung - Teil 331: Leistungsanforderungen und
d’essai pour les varistances à oxyde métallique (MOV) Prüfverfahren für Metalloxidvaristoren (MOV)
(IEC 61643-331:2017) (IEC 61643-331:2017)
This European Standard was approved by CENELEC on 2018-01-11. CENELEC members are bound to comply with the CEN/CENELEC
Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.
Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN-CENELEC
Management Centre or to any CENELEC member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CENELEC member into its own language and notified to the CEN-CENELEC Management Centre has the
same status as the official versions.
CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus, the Czech Republic,
Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden,
Switzerland, Turkey and the United Kingdom.

European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2018 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
Ref. No. EN IEC 61643-331:2018 E

European foreword
The text of document 37B/160/FDIS future edition 2 of IEC 61643-331, prepared by IEC/SC 37B:
“Specific components for surge arresters and surge protective devices”, of IEC/TC 37: “Surge
arresters”, was submitted to the IEC-CENELEC parallel vote and approved by CENELEC as EN IEC
61643-331:2018.
The following dates are fixed:
(dop) 2018-10-11
• latest date by which the document has to be
implemented at national level by
publication of an identical national
standard or by endorsement
• latest date by which the national (dow) 2021-01-11
standards conflicting with the
document have to be withdrawn
This document supersedes EN 61643-331:2003.

Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CENELEC shall not be held responsible for identifying any or all such patent rights.

Endorsement notice
The text of the International Standard IEC 61643-331:2017 was approved by CENELEC as a
European Standard without any modification.
In the official version, for Bibliography, the following notes have to be added for the standards indicated:

IEC 60068-2-6:2007 NOTE Harmonized as EN 60068-2-6:2008 (not modified).
IEC 60068-2-14:2009 NOTE Harmonized as EN 6008-2-14:2009 (not modified).
IEC 60068-2-29:1987 NOTE Harmonized as EN 6008-2-29:1993 (not modified).
IEC 60068-2-52:1996 NOTE Harmonized as EN 6008-2-52:1996 (not modified).
IEC 60060-1:2010 NOTE Harmonized as EN 60060-1:2010 (not modified).
IEC 61643-11:2011 NOTE Harmonized as EN 61643-11:2012 (not modified).
IEC 61051-1:2007 NOTE Harmonized as EN 61051-1:2008 (not modified).

Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications

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.
NOTE 1  Where an International Publication has been modified by common modifications, indicated by (mod), the relevant
EN/HD applies.
NOTE 2  Up-to-date information on the latest versions of the European Standards listed in this annex is available here:
www.cenelec.eu.
Publication Year Title EN/HD Year
IEC 60068-1 2013 Environmental testing -- Part 1: General EN 60068-1 2014
and guidance
IEC 60068-2-20 2008 Environmental testing -- Part 2-20: Tests - EN 60068-2-20 2008
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 - EN 60068-2-21 2006
Test U: Robustness of terminations and
integral mounting devices
IEC 60068-2-78 2012 Environmental testing -- Part 2-78: Tests - EN 60068-2-78 2013
Test Cab: Damp heat, steady state
IEC 61000-4-2 2008 Electromagnetic compatibility (EMC) -- Part EN 61000-4-2 2009
4-2: Testing and measurement techniques
- Electrostatic discharge immunity test
IEC 61643-11 (mod) 2011 Low-voltage surge protective devices -- EN 61643-11 2012
Part 11: Surge protective devices
connected to low-voltage power systems -
Requirements and test methods
- -  + A11 2018
IEC 61643-331 ®
Edition 2.0 2017-12
INTERNATIONAL
STANDARD
colour
inside
Components for low-voltage surge protective devices –

Part 331: Performance requirements and test methods for metal oxide varistors

(MOV)
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 31.040.20 ISBN 978-2-8322-5095-2

– 2 – IEC 61643-331:2017 © IEC 2017
CONTENTS
CONTENTS . 2
FOREWORD . 5
1 Scope . 7
2 Normative references . 7
3 Terms, definitions, symbols and abbreviated terms . 7
3.1 Ratings . 8
3.2 Characteristics . 9
3.3 Symbols . 10
3.4 Abbreviated terms . 11
4 Service conditions . 11
4.1 Operating and storage temperature ranges . 11
4.2 Altitude or atmospheric pressure range . 11
4.3 Relative Humidity . 11
5 Mechanical requirements and materials . 12
5.1 Robustness of terminations . 12
5.2 Solderability . 12
5.3 Marking . 12
6 General . 12
6.1 Failure rates . 12
6.2 Test standard atmospheric conditions . 12
7 Electrical requirements . 12
7.1 Nominal varistor voltage . 12
7.2 Maximum AC (DC) continuous operating voltage. 13
7.3 Standby current I . 13
DC
7.4 Capacitance . 13
7.5 Clamping voltage . 13
7.6 Electrostatic discharge (ESD) (for SMD type MOV only). 15
7.7 Rated impulse energy (W ) . 15
TM
7.8 Nominal discharge current I . 15
n
7.9 Endurance . 15
7.10 Limited current temporary overvoltage . 15
8 Standard design test criteria . 15
8.1 General . 15
8.2 Ratings . 15
8.2.1 Single-impulse maximum current (I ) . 15
TM
8.2.2 Next Impulse . 16
8.2.3 Continuous rated voltage (V ) . 16
M
8.3 Electrical characteristics . 16
8.3.1 Clamping voltage (V ) . 16
C
8.3.2 Standby current (I ) . 17
D
8.3.3 Nominal varistor voltage (V ) . 17
N
8.3.4 Capacitance (C ) . 17
V
8.4 Endurance . 18
8.5 ESD Test Method . 18
9 Nominal discharge current and limited current temporary overvoltage. 18

IEC 61643-331:2017 © IEC 2017 – 3 –
9.1 Thermally protected varistors – Sequence of tests . 18
9.2 Temperature and humidity cycle conditioning . 18
9.3 Nominal discharge current I(n) test description . 19
9.3.1 General . 19
9.3.2 Pass/fail criteria . 21
9.4 Limited current temporary overvoltage test description and procedure for
thermally protected varistors . 21
9.4.1 General . 21
9.4.2 Sample preparation . 21
9.4.3 Test conditions . 21
9.4.4 Pass/fail criteria . 22
9.5 Dielectric testing . 24
9.5.1 Test conditions . 24
9.5.2 Setup from foil to leads . 24
9.5.3 Pass criteria . 24
Annex A (informative) MOV testing according to IEC 61643-11:2011 – Surge
protective devices for the Class I, II and III . 25
A.1 General . 25
A.2 MOV selection . 25
A.3 Cross reference list of abbreviations, descriptions and definitions . 25
A.4 Operating duty test . 26
A.4.1 General . 26
A.4.2 Measured limiting voltage . 28
A.4.3 Class I and II operating duty tests (8.3.4.3) . 31
A.4.4 Additional duty test for test class I . 31
A.4.5 Class III operating duty tests . 32
A.4.6 Pass criteria for all operating duty tests and for the additional duty test
for test class I . 33
A.4.7 Preferred parameters of impulse discharge current I used for Class I

imp
additional duty tests . 33
A.4.8 Preferred values of impulse discharge current I used for Class I and
n
Class II residual voltage and operating duty tests . 33
A.4.9 Preferred values of combination waveshape used for Class III tests . 34
Annex B (informative) IEC 61051 Varistors for use in electronic equipment . 36
Annex C (informative) Accelerated endurance screening test . 37
C.1 Accelerated endurance screening test . 37
C.2 Preparation of sample . 37
C.3 Test conditions . 37
C.4 Pass criteria . 38
Annex D (informative) Proposed test method for determination of mean time to failure
(MTTF) . 39
D.1 Sampling plans . 39
D.2 Total test hours . 39
D.3 Samples. 39
D.4 Intermediate measurements . 40
D.5 Failure criteria . 40
D.6 Acceptance criteria . 40
Bibliography . 41

– 4 – IEC 61643-331:2017 © IEC 2017
Figure 1 – V-I characteristic of a MOV . 10
Figure 2 – Symbol for MOV . 10
Figure 3 – Symbol for thermally protected MOV . 11
Figure 4 – Test circuit for impulse peak current clamping voltage (V ) at peak impulse
C
current (I ) . 16
P
Figure 5 – Test circuit for measuring leakage current . 17
Figure 6 – Test circuit for measuring nominal varistor voltage (V ) . 17
V
Figure 7 – Nominal Discharge Current Flowchart . 20
Figure 8 – Sequence of the I Test . 21

n
Figure 9 – Temporary Overvoltage Limited Current test procedure Flowchart. 23
Figure A.1 – Flow chart of the operating duty test . 27
Figure A.2 – Test set-up for operating duty test . 28
Figure A.3 – Flow chart of testing to determine the measured limiting voltage . 30
Figure A.4 – Operating duty test timing diagram for test classes I and II . 31
Figure A.5 – Additional duty test timing diagram for test class I . 32
Figure A.6 – Operating duty test timing diagram for test class III . 32
Figure C.1 – Circuit of accelerated ageing test . 37
Figure D.1 – Test Circuit of MTTF . 40

Table 1 – Voltage ratings for disc types . 13
Table 2 – Typical Voltage Ratings for SMD types . 14
Table A.1 – Comparison of IEC 61643-11 and IEC 61643-311 . 26
Table A.2 – Preferred parameters for class I test . 33
Table A.3 – Preferred values for class I and class II tests . 34
Table A.4 – Preferred values for class III tests . 35
Table D.1 – Sampling plans . 39

IEC 61643-331:2017 © IEC 2017 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
COMPONENTS FOR LOW-VOLTAGE SURGE PROTECTIVE DEVICES –

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: Specific
components for surge arresters and surge protective devices, of IEC technical committee 37:
Surge arresters.
This second edition cancels and replaces the first edition published in 2003. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) Update of the nominal varistor voltage test method;
b) Addition of thermally protected varistors – component symbol and test methods;
c) Addition of nominal discharge current – test methods;
d) Addition of voltage ratings for disc types (Table 1);

– 6 – IEC 61643-331:2017 © IEC 2017
e) Addition of test currents for clamping voltage of disc types (Table 2);
f) Addition of typical voltage ratings of SMD types (Table 3); and
g) Addition of Limited current and temporary overvoltage tests for thermally protected
varistors.
The text of this International Standard is based on the following documents:
FDIS Report on voting
37B/160/FDIS 37B/164/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.
A bilingual version of this publication may be issued at a later date.

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.
IEC 61643-331:2017 © IEC 2017 – 7 –
COMPONENTS FOR LOW-VOLTAGE SURGE PROTECTIVE DEVICES –

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 line, or telecommunication, or
signalling circuits. They are designed to protect apparatus or personnel, or both, from high
transient voltages.
This specification applies to MOVs having two electrodes and hybrid overvoltage protection
components. This specification 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 60068-2-20:2008, 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 60068-2-78:2012, Environmental testing – Part 2-78: Tests – Test Cab: Damp heat,
steady state
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
3 Terms, definitions, symbols and abbreviated terms
For the purposes of this document, the following terms, definitions, symbols and abbreviated
terms 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

– 8 – IEC 61643-331:2017 © IEC 2017
3.1 Ratings
3.1.1
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: MODIFIED: IEC 62240-1:2013, Clause 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)]
3.1.2
single-impulse [transient] maximum current
I
TM
rated maximum value of current which may be applied for a single impulse of specified
waveform
Note 1 to entry: For power distribution surge protective devices (SPDs), IEC 61643-11, Maximum Discharge
Current I is used.
MAX
3.1.3
nominal discharge current
I
n
crest value of the current through the MOV having a current waveshape of 8/20
3.1.4
impulse life characteristic
graphical representation between impulse current peak (I), equivalent rectangular pulse width
(T), and impulse numbers (n) for which the varistor 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 temperature derating curve.
3.1.5
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.
3.1.6
single-pulse [transient] maximum energy
W
TM
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).
3.1.7
maximum continuous voltage
V
M
voltage that may be applied continuously at a specified temperature
Note 1 to entry: May also be called U or maximum continuous operating voltage (MCOV).

C
Note 2 to entry: See Figure 1.

IEC 61643-331:2017 © IEC 2017 – 9 –
3.1.8
maximum continuous AC voltage
V
M(AC)
value of rms. power frequency voltage (less than 5 % total harmonic distortion) that may be
applied continuously at a specified temperature
3.1.9
maximum continuous DC voltage
V
M(DC)
DC voltage that may be applied continuously at a specified temperature
3.1.10
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
3.2 Characteristics
3.2.1
characteristic
inherent and measurable property of an MOV
3.2.2
standby current
I
D
current passing through MOV at maximum continuous voltage V
M
Note 1 to entry: The current passing through the MOV at less than V is called leakage current.
M
3.2.3
nominal varistor voltage
V
N
voltage across the MOV measured at a specified current of specific duration
Note 1 to entry: See Figure 1.
3.2.4
clamping voltage
V
C
peak voltage across the MOV measured under conditions of a specified peak pulse current
(I ) and specified waveform
P
Note 1 to entry: See Figure 1.
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.
C
3.2.5
capacitance
C
V
capacitance across the MOV measured at a specified frequency, voltage and time
3.2.6
metal oxide varistor
MOV
component whose conductance, at a given temperature, increases rapidly with voltage
Note 1 to entry: This is also known as a voltage dependant resistor (VDR).

– 10 – IEC 61643-331:2017 © IEC 2017
3.2.7
thermally protected metal oxide varistor
varistor which includes a series non-resettable element that will disconnect the MOV when it
is overheated due to excessive dissipation
+ i
I
TM
I
p
I
N
I
D
-v +v
V V V
M V C
- i IEC
Figure 1 – V-I characteristic of an MOV
3.3 Symbols
Figures 2 and 3 represent the IEC 60617 symbols for MOV and thermally protected MOV,
respectively.
U
IEC
Figure 2 – Symbol for MOV
IEC 61643-331:2017 © IEC 2017 – 11 –
θ
Monitor lead
U
IEC
Figure 3 – Symbol for thermally protected MOV
NOTE IEC 60027 recommends the letters V and v only as reserve symbols for voltage; however, in the field of
MOV components, these are so widely used that in this publication they are preferred to U and u.
3.4 Abbreviated terms
DUT Device Under Test
ESD Electrostatic Discharge
MCOV Maximum Continuous Operating Voltage
MOV Metal Oxide Varistor
MTTF Mean Time To Failure
SMD Surface Mount Device
SPD Surge Protective Device
VDR Voltage Dependent Resistor
4 Service conditions
4.1 Operating and storage temperature ranges
Operating range
– Normal: –5 °C to +55 °C
– Extended: −40 °C to +85 °C
Storage range MOV
– Normal: –40 °C to +85 °C
– Extended: −40 °C to +125 °C
Storage range thermally protected MOV
– Normal: –40 °C to +85 °C
– Extended: −40 °C to +85 °C
4.2 Altitude or atmospheric pressure range
The altitude of air pressure is within 80 kPa to 106 kPa (refer to IEC 60068-1).
4.3 Relative Humidity
Normal range: 5 % to 95 % at 25 °C (refer to IEC 60068-1 and IEC 60068-2-78).

– 12 – IEC 61643-331:2017 © IEC 2017
5 Mechanical requirements and materials
5.1 Robustness of terminations
If applicable, the user shall specify a suitable test from IEC 60068-2-21.
5.2 Solderability
Solder terminations shall meet the requirements of IEC 60068-2-20, test Ta, method 1.
5.3 Marking
Legible and permanent marking shall be applied to the MOV as necessary to ensure that the
user can determine the following information by inspection:
Each MOV shall be marked with the following information:
Date of manufacture or batch number
Manufacturer name or trademark
Part number
Safety approval markings
NOTE 1 The necessary information can also be coded.
When the space is not sufficient for printing this data, it should be provided in the technical
documentation after agreement between the manufacturer and the purchaser.
6 General
6.1 Failure rates
Sampling size, electrical characteristics to be tested, etc. should be covered by the quality
assurance requirements, which are not covered by this document.
6.2 Test standard atmospheric conditions
The following tests shall be performed on the MOVs as required by the application. Unless
otherwise specified, ambient test conditions shall be as follows:
• temperature: 15 °C to 35 °C;
• relative humidity: 25 % to 75 %;
MOVs of various types should have the characteristics listed in Table 1 when tested in
accordance with Clause 8.
7 Electrical requirements
7.1 Nominal varistor voltage
When tested according to 8.3.3, varistor voltage should be within the specified manufacturer’s
limits. Table 1 shows the nominal varistor voltages of high voltage and low voltage disc types
that are commonly used; their allowable tolerances are ±10 %.
The nominal varistor voltages and tolerances listed in Table 2 are typical for surface mount
Device (SMD) types.
IEC 61643-331:2017 © IEC 2017 – 13 –
7.2 Maximum AC (DC) continuous operating voltage
Unless otherwise specified, MOVs shall have a maximum AC (DC) continuous voltage
V /V as given in Tables 1 and 2, the conformity shall be evaluated according to 8.2.3.
M(AC) M(DC)
NOTE Maximum AC (DC) continuous operating voltage is sometimes referred to as U .
C
7.3 Standby current I
DC
When tested according to 8.3.2, the standby current, DC, under maximum continuous DC
voltage V , shall be less than the maximum value specified by the manufacturer and there
DC
shall be no upward drifting during the application of the test voltage V .
DC
7.4 Capacitance
When tested according to 8.3.4, the measured value of capacitance shall not exceed the
value specified by the manufacturer.
7.5 Clamping voltage
The measured clamping voltage (see 8.3.1) at a specified impulse current shall be no more
than the specified values or the values indicated in Tables 1 and 2. Unless otherwise
specified, 8/20 impulse current having the peak as specified in shall be used.
NOTE Clamping voltage V is referred to as Measured Limiting Voltage in IEC 61643-11.
C
Table 1 – Typical voltage ratings for disc types
Max. continuous voltage (V ) Clamping voltage (Note), V (V)
Nominal varistor M C
voltage V (V)
N AC (rms) V /V DC V 8/20, V
M(AC) M(DC)
DC C
18 11 14 36
22 14 18 43
27 17 22 53
33 20 26 65
39 25 31 77
47 30 38 93
56 35 45 110
68 40 56 135
82 50 65 135
100 60 85 165
120 75 100 200
150 95 125 250
180 115 150 300
200 130 170 340
220 140 180 360
240 150 200 395
275 175 225 455
300 195 250 505
330 210 270 545
360 230 300 595
390 250 320 650
430 275 350 710
– 14 – IEC 61643-331:2017 © IEC 2017
Max. continuous voltage (V ) Clamping voltage (Note), V (V)
Nominal varistor M C
voltage V (V)
N AC (rms) V /V DC V 8/20, V
M(AC) M(DC)
DC C
470 300 385 775
510 320 410 845
560 350 450 930
620 385 505 1 025
680 420 560 1 120
715 440 585 1 180
750 460 615 1 240
820 510 670 1 355
910 550 745 1 500
1 000 625 825 1 650
1 100 680 895 1 815
1 200 750 970 2 000
1 600 1 000 1 280 2 650
1 800 1 100 1 465 2 970
NOTE Clamping voltage V is referred to as Measured Limiting Voltage in IEC 61643-11.
C
Table 2 – Typical voltage ratings for SMD types
Nominal varistor Maximum continuous voltage (V )
M
Voltage V (V) AC (rms) V DC V
N AC DC
5,6 ± 20 % 2,5 4
6,8± 20 % 3,5 4,5
8,2 ± 20 % 4 5,5
10 ± 20 % 5 7
12± 20 % 6 8,5
15± 20 % 7,5 10,5
18 ± 20 % 9 13
22 ± 10 % 14 18
27 ± 10 % 17 22
33 ± 10 % 20 26
39 ± 10 % 25 31
47 ± 10 % 30 38
56 ± 10 % 35 45
68 ± 10 % 40 56
82 ± 10 % 50 65
NOTE Clamping voltage V is referred to as Measured Limiting Voltage in
C
IEC 61643-11.
During the tests, there shall be no flashover or puncture of the samples, the MOV voltage of
the samples shall be tested prior to and after the tests, the change of which shall not exceed
±10 %, when tested according to 8.3.3.

IEC 61643-331:2017 © IEC 2017 – 15 –
7.6 Electrostatic discharge (ESD) (for SMD type MOV only)
The SMD MOVs shall be subjected to electrostatic discharge (ESD) contact discharge test of
8 kV for 10 applications with an interval of 1 s according to 8.5.
During the tests, there shall be no evidence of flashover or puncture of the samples, and the
Varistor voltage of the samples shall be tested prior to and after the tests, the change of
which shall not exceed ±30 %.
7.7 Rated impulse energy (W )
TM
The MOV shall be capable of absorbing the impulse energy specified by the manufacturer
when subjected to one impulse current of 2 ms or 10/1000 wave and tested according to
8.2.1.
7.8 Nominal discharge current I
n
The MOV shall be subjected to 15 applications of impulse currents of 8/20 wave with the peak
specified by the manufacturer, and tested according to 9.3.
7.9 Endurance
The MOV used for power supply circuitry shall be subjected to an endurance test under the
conditions of maximum operating temperature and maximum continuous operating voltage for
1 000 h and tested according to 8.4.
If all concerned parties agree the optional accelerated endurance screening test in Annex C
may be used.
7.10 Limited current temporary overvoltage
This is an AC step stress test to evaluate MOV components for potential ignition sources
when the component is subjected to a.c. overload, (see 9.4).
8 Standard design test criteria
8.1 General
The design tests described in 8.3 provide standardized methods for measuring specified
characteristics of a MOV for the purpose of component selection for a surge protective device
(SPD). These characteristics may vary from MOV to MOV, making it necessary to measure all
components to be selected for a SPD. MOVs are bi-directional and they shall be tested with
both positive and negative voltages.
8.2 Ratings
8.2.1 Single-impulse maximum current (I )
TM
In the absence of specified requirements, the test current shall be an 8/20 waveshape.
NOTE See Figure 4.
– 16 – IEC 61643-331:2017 © IEC 2017
S1 S2 L
R2
R1
V
V
PS C R3 MOV OSC
I
R4
IEC
Components
C Energy storage capacitor R3 Impulse-shaping resistor
L Impulse-shaping inductor R2 Impulse-shaping and current-limiting resistor
MOV Device under test (MOV) R4 Current-sensing resistor (coaxial). Alterna-
tively, a current transformer probe of adequate
rating may be used
OSC Oscilloscope for observing current and S1 Charging switch
voltage
PS DC charging power supply S2 Discharge switch
R1 Charging resistor
Caution: The circuit shown is for description only; Measurement techniques for high-current and high-frequency
testing should be observed, such as four-point Kelvin contact, differential oscilloscope, short leads, etc.

Figure 4 – Test circuit for single-impulse maximum current
8.2.2 Next Impulse
The next impulse shall be applied after the device under test (DUT) has returned to thermal
equilibrium (for example, the initial conditions before the impulses were applied). In the
absence of specified requirements, the test current shall be an 8/20 waveshape.
NOTE 1 MOVs intended for service in IEC 61643-11 surge protective devices require special class I, class II and
class III testing procedures and waveforms. These tests are covered in Annex A.
NOTE 2 See Figure 4.
8.2.3 Continuous rated voltage (V )
M
This rating is verified in 8.3.2.
8.3 Electrical characteristics
8.3.1 Clamping voltage (V )
C
Maximum clamping voltage shall be measured during the single impulse current (I ), see
C
clause 8.2.1. The peak clamping voltage and peak test current are not necessarily coincident
in time. In the absence of specified requirements, the test current shall be an 8/20
waveshape.
NOTE 1 MOVs intended for service in IEC 61643-11 surge protective devices require special class II or class III
testing pro
...