IEC 61051-2:2021

IEC 61051-2 ®
Edition 2.0 2021-11
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Varistors for use in electronic equipment –
Part 2: Sectional specification for surge suppression varistors

Varistances utilisées dans les équipements électroniques –
Partie 2: Spécification intermédiaire pour varistances pour limitations de
surtensions transitoires
All rights reserved. Unless otherwise specified, 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
either IEC or IEC's member National Committee in the country of the requester. If you have any questions about IEC
copyright or have an enquiry about obtaining additional rights to this publication, please contact the address below or
your local IEC member National Committee for further information.

Droits de reproduction réservés. Sauf indication contraire, aucune partie de cette publication ne peut être reproduite
ni utilisée sous quelque forme que ce soit et par aucun procédé, électronique ou mécanique, y compris la photocopie
et les microfilms, sans l'accord écrit de l'IEC ou du Comité national de l'IEC du pays du demandeur. Si vous avez des
questions sur le copyright de l'IEC ou si vous désirez obtenir des droits supplémentaires sur cette publication, utilisez
les coordonnées ci-après ou contactez le Comité national de l'IEC de votre pays de résidence.

IEC Central Office Tel.: +41 22 919 02 11
3, rue de Varembé info@iec.ch
CH-1211 Geneva 20 www.iec.ch
Switzerland
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 IEC online collection - oc.iec.ch
The advanced search enables to find IEC publications by a Discover our powerful search engine and read freely all the
variety of criteria (reference number, text, technical publications previews. With a subscription you will always
committee, …). It also gives information on projects, replaced have access to up to date content tailored to your needs.
and withdrawn publications.
Electropedia - www.electropedia.org
IEC Just Published - webstore.iec.ch/justpublished
The world's leading online dictionary on electrotechnology,
Stay up to date on all new IEC publications. Just Published
containing more than 22 000 terminological entries in English
details all new publications released. Available online and
and French, with equivalent terms in 18 additional languages.
once a month by email.
Also known as the International Electrotechnical Vocabulary

(IEV) online.
IEC Customer Service Centre - webstore.iec.ch/csc
If you wish to give us your feedback on this publication or
need further assistance, please contact the Customer Service
Centre: sales@iec.ch.
A propos de l'IEC
La Commission Electrotechnique Internationale (IEC) est la première organisation mondiale qui élabore et publie des
Normes internationales pour tout ce qui a trait à l'électricité, à l'électronique et aux technologies apparentées.

A propos des publications IEC
Le contenu technique des publications IEC est constamment revu. Veuillez vous assurer que vous possédez l’édition la
plus récente, un corrigendum ou amendement peut avoir été publié.

Recherche de publications IEC - IEC online collection - oc.iec.ch
webstore.iec.ch/advsearchform Découvrez notre puissant moteur de recherche et consultez
La recherche avancée permet de trouver des publications IEC gratuitement tous les aperçus des publications. Avec un
en utilisant différents critères (numéro de référence, texte, abonnement, vous aurez toujours accès à un contenu à jour
comité d’études, …). Elle donne aussi des informations sur adapté à vos besoins.
les projets et les publications remplacées ou retirées.

Electropedia - www.electropedia.org
IEC Just Published - webstore.iec.ch/justpublished
Le premier dictionnaire d'électrotechnologie en ligne au
Restez informé sur les nouvelles publications IEC. Just
monde, avec plus de 22 000 articles terminologiques en
Published détaille les nouvelles publications parues.
anglais et en français, ainsi que les termes équivalents dans
Disponible en ligne et une fois par mois par email.
16 langues additionnelles. Egalement appelé Vocabulaire

Electrotechnique International (IEV) en ligne.
Service Clients - webstore.iec.ch/csc

Si vous désirez nous donner des commentaires sur cette
publication ou si vous avez des questions contactez-nous:
sales@iec.ch.
IEC 61051-2 ®
Edition 2.0 2021-11
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Varistors for use in electronic equipment –

Part 2: Sectional specification for surge suppression varistors

Varistances utilisées dans les équipements électroniques –

Partie 2: Spécification intermédiaire pour varistances pour limitations de

surtensions transitoires
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 31.040.20 ISBN 978-2-8322-1045-7

– 2 – IEC 61051-2:2021 © IEC 2021
CONTENTS
FOREWORD . 4
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 7
4 Preferred characteristics . 7
4.1 Climatic categories . 7
4.2 Voltage ratings . 7
4.3 Derating for metal oxide varistors. 9
4.3.1 General . 9
4.3.2 Derating at increased operating temperatures . 9
4.3.3 Maximum peak current derating characteristic . 10
5 Test procedures, test severities and performance requirements . 11
5.1 General . 11
5.2 Visual examination and check of dimensions . 11
5.3 Electrical tests . 11
5.3.1 Varistor voltage . 11
5.3.2 Leakage current . 11
5.3.3 Capacitance . 11
5.3.4 Voltage proof . 11
5.3.5 Clamping voltage . 11
5.3.6 Maximum peak current . 11
5.3.7 Rated energy . 11
5.4 Soldering test. 12
5.4.1 Resistance to soldering heat . 12
5.4.2 Solderability. 12
5.5 Temperature and climate test . 12
5.5.1 Damp heat, steady state . 12
5.5.2 Endurance at upper category temperature . 12
5.5.3 Rapid change of temperature . 12
5.5.4 Climatic sequence . 12
5.6 Robustness test . 12
5.6.1 Robustness of terminations . 12
5.6.2 Shock testing . 12
5.6.3 Vibration . 13
5.6.4 Solvent resistance of marking . 13
5.7 Fire hazard (Needle flame test) . 13
6 Marking, packaging and ordering information . 13
7 Detail specifications . 13
7.1 General . 13
7.2 Outline drawing and dimensions . 13
7.3 Mounting . 14
7.4 Ratings and characteristics . 14
7.5 Marking . 14
7.6 Ordering information . 14
8 Quality assessment procedure . 14
8.1 General . 14

8.2 Primary stage of manufacturer . 14
8.3 Structurally similar components . 14
8.4 Qualification approval (QA) . 15
8.4.1 Qualification approval (QA) procedures . 15
8.4.2 Fixed sample size procedure . 15
8.4.3 Test schedule . 15
8.5 Quality conformance inspection . 19
8.5.1 General . 19
8.5.2 Formation of inspection lots . 19
8.5.3 Test schedule . 19
8.5.4 Assessment level . 19
Annex X (informative) Cross-references to the previous edition of this document . 21

Figure 1 – Typical temperature derating curve for maximum continuous voltage, surge
current, energy absorption and average power dissipation . 10
Figure 2 – Typical maximum peak current derating curve . 10

Table 1 – Upper and lower category temperature and duration of the damp heat,
steady state test . 7
Table 2 – Preferred voltage ratings for disk type varistors . 8
Table 3 – Preferred voltage ratings for SMD types . 9
Table 4 – Test schedule for the qualification approval . 16
Table 5 – Test schedule for the qualification approval . 20
Table 6 – Periodic inspection . 20
Table X.1 – Cross-references . 21

– 4 – IEC 61051-2:2021 © IEC 2021
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
VARISTORS FOR USE IN ELECTRONIC EQUIPMENT –

Part 2: Sectional specification for surge suppression varistors

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.
IEC 61051-2 has been prepared by IEC technical committee 40: Capacitors and resistors for
electronic equipment. It is an International Standard.
This second edition cancels and replaces the first edition published in 1991 and
Amendment 1:2009. This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) revision for the structure in accordance with ISO/IEC Directives, Part 2) to the extent
practicable, and for harmonizing with IEC 61051-1:2018;
b) Annex X has been added for comparison with the previous edition;
c) two lists of preferred voltage ratings for disk type and SMD type varistors have been added;
d) permissible numbers of non-conforming items have been set to zero (zero fault) in the test
schedule in 8.4.3.
The text of this International Standard is based on the following documents:
Draft Report on voting
40/2877/FDIS 40/2895/RVD
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this International Standard is English.
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/standardsdev/publications.
A list of all parts in the IEC 61051 series, published under the general title Varistors for use in
electronic equipment, 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 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 document 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.

– 6 – IEC 61051-2:2021 © IEC 2021
VARISTORS FOR USE IN ELECTRONIC EQUIPMENT –

Part 2: Sectional specification for surge suppression varistors

1 Scope
This part of IEC 61051 is a sectional specification and is applicable to metal oxide varistors with
symmetrical voltage-current characteristics for use in electronic equipment connected to any
AC or DC supply system.
These varistors are designed to protect electronic and other sensitive equipment from high
transient surges. Varistors under the scope of this sectional specification are not intended to
give primary protection against lightning surges.
These varistors have metallic connections and are intended to be mounted as through hole
component or directly on to printed boards.
The object of this document is to prescribe preferred ratings and characteristics and to select
from IEC 61051-1 the appropriate quality assessment procedures, tests and measuring
methods, and to give general performance requirements for this type of varistors.
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 60062, Marking codes for resistors and capacitors
IEC 60068-1, Environmental testing – Part 1: General and guidance
IEC 60068-2-1, Environmental testing – Part 2-1: Tests – Test A: Cold
IEC 60068-2-2, Environmental testing – Part 2-2: Tests – Test B: Dry heat
IEC 60068-2-6, Environmental testing – Part 2-6: Tests – Test Fc: Vibration (sinusoidal)
IEC 60068-2-20, Environmental testing – Part 2-20: Tests – Test Ta and Tb: Test methods for
solderability and resistance to soldering heat of devices with leads
IEC 60068-2-27, Environmental testing – Part 2-27: Tests – Test Ea and guidance: Shock
IEC 60068-2-30, Environmental testing – Part 2-30: Tests – Test Db: Damp heat, cyclic (12 h +
12 h cycle)
IEC 60068‑2‑45, Basic environmental testing procedures – Part 2-45: Tests – Test XA and
guidance: Immersion in cleaning solvents
IEC 60695-11-5, Fire hazard testing – Part 11-5: Test flames – Needle-flame test method –
Apparatus, confirmatory test arrangement and guidance

IEC 61051-1:2018, Varistors for use in electronic equipment – Part 1: Generic specification
IEC 61051-2-2, Varistors for use in electronic equipment – Part 2: Blank detail specification for
zinc oxide surge suppression varistors. Assessment level E
IEC 61193-2:2007, Quality assessment systems – Part 2: Selection and use of sampling plans
for inspection of electronic components and packages
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 61051-1 apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
4 Preferred characteristics
4.1 Climatic categories
The varistors covered by this specification are classified into climatic categories according to
the general rules given in IEC 60068-1.
The upper and lower category temperatures and the duration of the damp-heat steady-state
test shall be selected from Table 1.
Table 1 – Upper and lower category temperature and duration
of the damp heat, steady state test
Lower category temperature [°C] −55, −40, −25, −10
Upper category temperature [°C] +70, +85, +100, +105, +125, +155
a
4, 10, 21, 56
Duration of damp heat, steady state test [days]
a
Not applicable to unprotected types which have a -/-/00 category.

4.2 Voltage ratings
Table 2 and Table 3 provide preferred voltage ratings for disk type varistors and SMD type
varistors.
– 8 – IEC 61051-2:2021 © IEC 2021
Table 2 – Preferred voltage ratings for disk type varistors
b
Varistor Clamping voltage ,
Max. continuous voltage
voltage U U
V CLP
a
(V)  (V)
U U 8/20, U
RMS DCM CLP
(V) (V)
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
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
a
Unless otherwise specified, measured at 1 mA
b
measured at class current which is given by detail specification

Table 3 – Preferred voltage ratings for SMD types
Varistor Maximum continuous voltage
Voltage U
U U
V
RMS DCM
(V) (V) (V)
(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
4.3 Derating for metal oxide varistors
4.3.1 General
Derating is the intentional reduction of maximum ratings in the application of a device. For metal
oxide varistors derating is of particular interest under the following conditions:
• derating at increased operating temperatures;
• derating for repetitive maximum peak current.
4.3.2 Derating at increased operating temperatures
For operating temperatures exceeding the maximum operating temperature as specified in the
component specification, the following operating conditions of varistors may be derated as
demonstrated in Figure 1:
• maximum continuous voltage;
• surge current;
• energy absorption;
• average power dissipation.
– 10 – IEC 61051-2:2021 © IEC 2021

Figure 1 – Typical temperature derating curve for maximum continuous voltage,
surge current, energy absorption and average power dissipation
4.3.3 Maximum peak current derating characteristic
A typical feature of metal oxide varistors is the dependence of the maximum permissible ratings
for surge current, and thus for energy absorption, on the pulse shape, pulse duration, and the
number of times this load is repeated during the overall lifetime of the varistor.
IEC 61051-1:2018, Clause C.2 applies.

Figure 2 – Typical maximum peak current derating curve

5 Test procedures, test severities and performance requirements
5.1 General
Test severities and requirements prescribed by detail specifications referring to this sectional
specification shall be of equal or superior performance level. Inferior performance levels are
not permitted.
The severities for the tests shall be prescribed by the detail specifications, following the
prescriptions of the generic specification IEC 61051-1 and Clause 5 (Test procedures, test
severities and performance requirements) of this sectional specification.
5.2 Visual examination and check of dimensions
IEC 61051-1:2018, 6.4 applies.
Visual examination shall be carried out with suitable equipment with approximately 10×
magnification and lighting appropriate to the specimen under test and the quality level required.
The operator should have facilities available for incident or transmitted illumination as well as
an appropriate measuring facility.
5.3 Electrical tests
5.3.1 Varistor voltage
IEC 61051-1:2018, 6.6 applies.
Usually, the varistor voltage will be measured at a current of 1 mA. If conditions are different
from IEC 61051-1:2018, 6.6, they shall be prescribed in the detail specification.
5.3.2 Leakage current
IEC 61051-1:2018, 6.7 applies.
5.3.3 Capacitance
IEC 61051-1:2018, 6.8 applies.
5.3.4 Voltage proof
IEC 61051-1:2018, 6.9 applies.
5.3.5 Clamping voltage
IEC 61051-1:2018, 6.11 applies.
5.3.6 Maximum peak current
IEC 61051-1:2018, 6.13 applies.
The pulse current test and the combination pulse test are considered to be alternative. The
detail specification shall indicate which test is performed.
5.3.7 Rated energy
IEC 61051-1:2018, 6.15 applies.

– 12 – IEC 61051-2:2021 © IEC 2021
5.4 Soldering test
5.4.1 Resistance to soldering heat
IEC 61051-1:2018, 6.18 applies.
± 5) ° C, 10 s applies.
IEC 60068-2-20:2008, Test Tb, Method 1, solder bath conditions: (260
5.4.2 Solderability
IEC 61051-1:2018, 6.19 applies.
IEC 60068-2-20, Test Ta, Method 1 Soldering bath conditions: Pb- free solder: (245 ± 3) °C,
3 s applies.
5.5 Temperature and climate test
5.5.1 Damp heat, steady state
IEC 61051-1:2018, 6.24 applies.
5.5.2 Endurance at upper category temperature
IEC 61051-1:2018, 6.26 applies.
5.5.3 Rapid change of temperature
IEC 61051-1:2018, 6.20 applies.
5.5.4 Climatic sequence
IEC 61051-1:2018, 6.23 applies.
5.6 Robustness test
5.6.1 Robustness of terminations
IEC 61051-1:2018, 6.17 applies.
5.6.2 Shock testing
5.6.2.1 General
IEC 61051-1:2018, 6.21 applies.
There are two grades of severity which are considered to be alternative.
5.6.2.2 Shock
The following test conditions (shock) apply:
IEC 60068-2-27:2008, Test Ea, Pulse shape: half-sine, A = 500 m/s , D = 11 ms.
The following test severity applies:
3 successive shocks in each direction (6 × 3 shocks), with separate specimens to be used each
direction.
The mounting shall be such that there shall be no parasitic vibration.

5.6.2.3 Repetitive shock
The following test conditions (repetitive shock) apply:
IEC 60068-2-27:2008, Test Ea, Pulse shape: half-sine, A = 400 m/s , D = 6 ms.
The following test severity applies:
5 000 successive shocks in each direction (6 × 5 000 shocks), with separate specimens to be
used each direction
The mounting shall be such that there shall be no parasitic vibration.
5.6.3 Vibration
IEC 61051-1:2018, 6.22 applies.
The following test conditions apply:
IEC 60068-2-6:2007, Test Fc, Frequency range: 10 Hz to 55 Hz, A = 0,75 mm or 98 m/s
(whichever is the less), D = 3 × 2 h.
The mounting shall be such that there shall be no parasitic vibration.
5.6.4 Solvent resistance of marking
IEC 61051-1:2018, 6.27 applies.
5.7 Fire hazard (Needle flame test)
IEC 61051-1:2018, 6.25 applies.
6 Marking, packaging and ordering information
Marking, requirement on packaging and ordering information shall be provided by the detail
specification (see 7.5 and 7.6).
7 Detail specifications
7.1 General
Detail specifications shall be derived from the relevant blank detail specification.
Detail specifications shall not specify requirements inferior to those of the generic, sectional or
blank detail specification. When more severe requirements are included, they shall be listed in
the detail specification and indicated in the test schedules, for example, by an asterisk.
The following information shall be given in each detail specification and the values quoted
shall preferably be selected from those given in the appropriate clause of this sectional
specification.
7.2 Outline drawing and dimensions
There shall be an illustration of the varistor as an aid to easy recognition and for comparison
of the varistor with others. Dimensions and their associated tolerances, which affect
interchangeability and mounting, shall be given in the detail specification. All dimensions
shall preferably be stated in millimetres, however, when the original dimensions are given
in inches, the converted metric dimensions in millimetres shall be added.

– 14 – IEC 61051-2:2021 © IEC 2021
Normally the numerical values shall be given for the length, width and height of the body
and the wire spacing or for cylindrical types the body diameter, and the length and diameter
of the terminations. When necessary, for example when in a detail specification more than
one style is covered, the dimensions and their associated tolerances shall be placed in a
table below the drawing.
When the configuration is other than described above, the detail specification shall state
such dimensional information as will adequately describe the varistor. When the varistor
is not designed for use on printed boards, this shall be clearly stated in the detail
specification.
7.3 Mounting
The detail specification shall specify the method of mounting to be applied for normal use and
for the application of the vibration and the bump or shock tests. The varistors shall be mounted
by their normal means. The design of the varistor may be such that special mounting fixtures
are required in its use. In this case, the detail specification shall describe the mounting fixtures
and they shall be used in the application of the vibration and bump or shock tests. For the latter
tests, the mounting shall be such that there shall be no parasitic vibration.
7.4 Ratings and characteristics
The ratings and characteristics shall be in accordance with the relevant clauses of this
specification.
7.5 Marking
IEC 61051-1: 2018, 4.3 applies.
The detail specification shall specify the content of the marking on the varistor and on the
package.
7.6 Ordering information
The detail specification shall specify the ordering information.
When coding is used, the method shall be preferably selected from those given in IEC 60062.
8 Quality assessment procedure
8.1 General
IEC 61051-1:2018, Clause 5 applies.
8.2 Primary stage of manufacturer
The primary stage of manufacture is defined as the initial mixing process of ingredients.
8.3 Structurally similar components
IEC 61051-1:2018, 5.4 applies.
Varistors within the scope of this specification may be grouped as structurally similar for the
purpose of forming inspection lots provided that the following requirements are met:
a) They shall be produced by one manufacturer on one site using essentially the same design,
materials, processes and methods;

b) For electrical tests, devices having the same electrical characteristics may be grouped
provided that the element determining the characteristics is similar for all the devices
concerned;
c) For environmental tests, devices having the same encapsulation, basic internal structure
and finishing processes may be grouped;
d) For visual inspection (except marking) devices may be grouped if they have been made on
the same production line, have the same dimensions encapsulation and external finish;
The grouping may also be used for robustness of terminations and soldering tests where it
is convenient to group devices with different internal structures (see item c) above);
e) For endurance tests, devices may be grouped if they have been made with the same
production process in the same location using the same design and differing only in
electrical characteristics. If it can be shown that one type from the group is more heavily
stressed than the others, then tests on this type may be accepted for the remaining members
of the group.
8.4 Qualification approval (QA)
8.4.1 Qualification approval (QA) procedures
The procedures for qualification approval testing are given in the Generic Specification,
IEC 61051-1:2018, 5.5.
The schedule to be used for qualification approval testing on the basis of lot-by-lot and periodic
testing is given in 8.5 of this document.
The procedure using a fixed sample size schedule is given in 8.4.2 and 8.4.3.
8.4.2 Fixed sample size procedure
The fixed sample size procedure is described in IEC 61051-1:2018, 5.5.3 b).
The sample shall be representative of the range of values for which the approval is sought to.
This may or may not be the complete range covered by the detail specification. The proportion
of specimens having the different characteristics shall be proposed by the manufacturer's chief
inspector and shall be to the satisfaction of the national supervising inspectorate.
When additional groups are introduced into the qualification approval test schedule, the number
of specimens required for Group "0" shall be increased by the same number as that required
for the additional groups.
8.4.3 Test schedule
The complete series of tests specified in Table 4 are required for the approval of varistors
covered by one detail specification. The tests of each group shall be carried out in the given
order.
The whole sample shall be subjected to the tests of Group “0” and the divided for the other
groups. For insulated varistors, the tests of Group 1 shall be made before the tests of Groups
2 to 7.
Specimens found defective during the tests of Group "0" shall not be used for the other groups.
"One defective" is counted when a varistor has not satisfied the whole or a part of the tests of
a group.
– 16 – IEC 61051-2:2021 © IEC 2021
The approval is granted when the number of defectives does not exceed the specified number
of permissible defectives for each group or sub-group and the total number of permissible
defectives.
Table 4 – Test schedule for the qualification approval
a a a
Sample Test Subclause Conditions of test Performance
D or n c
Group of a requirements
ND
No. 61051‑1:2018
0 Sample Group 0 ND 56 + 4 0
Visual examination 6.4.1
Legible marking and as
Marking 6.4.2
specified in the detail
specification
Dimensions 6.4.3 gauging As specified in the detail
specification
Varistor voltage 6.6 At specified current As specified in the detail
specification
Leakage current 6.7 At maximum continuous As specified in the detail
DC voltage, at 25°C specification

1 Group 1 D 8 0
Maximum peak current 6.13 10 current pulses (8 µs Visual inspection:
/20 µs) of same polarity, No visual damage
frequency: 2 per min
Leakage current or voltage
at specified current as
or
specified in the detail
specification
10 pulses of combination
wave generator, with
same polarity,
frequency: 1 per min
As specified in the detail
Clamping voltage 6.11 At class current
specification
Voltage proof 6.9 (Insulated varistors only) As specified in the detail
specification
Method: As specified in
the detail specification
2 Group 2 D 8 0
Robustness of 6.17 Test appropriate to the Visual inspection:
terminations type of termination No visual damage
Leakage current or voltage
at specified current as
specified in the detail
specification
If applicable As specified in the detail
Solderability 6.19
specification
Solder bath method or
other appropriate method
Solvent resistance of As specified in detail
6.27 Legible marking
marking specification
Solvent: IEC 60068‑2‑45
Solvent temperature:
23°C
Conditioning method 1
Rubbing material: cotton
wool
Recovery time: not
applicable
a a a
Sample Test Subclause Conditions of test Performance
D or n c
Group of a requirements
ND
No. 61051‑1:2018
3 Group 3 D 8
Dimensions (detail) 6.4.4 As specified in the detail
specification
Leakage current 6.7 At upper category As specified in the detail
temperature and at other specification
temperature(s) as
specified in the detail
specification
Rated energy 6.15 Single current pulse with Visual inspection:
2 ms rectangular wave No visual damage
shape or 10 µs /1 000 µs
Leakage current or voltage
wave shape
at specified current as
specified in the detail
specification
4 Group 4 D 8 0
Damp heat, steady 6.24 4 specimens: Visual inspection:
state No visual damage and the
No voltage applied
marking shall be legible
Other 4 specimens:
Leakage current or voltage
Applied voltage: at specified current as
specified in the detail
10 % of U
DCM
specification
Insulation resistance as
specified in the detailed
specification
5 Group 5A D 8 0
Half of the samples of
group 5
as specified in the detailed
Capacitance 6.8 f = 1 kHz
specification
signal level ≤ 1 V .
RMS
zero bias
Resistance to 6.18 IEC 60068-2-20, Test Tb, Visual inspection:
soldering heat (if No visual damage
Method 1
applicable)
Leakage current or voltage
T = (260 ± 5) °C,
at specified current as
D = (10 ± 1) s
specified in the detail
specification
Component solvent 6.28 As specified in detail Visual inspection:
resistance specification No visual damage
Solvent: IEC 60068‑2‑45 Leakage current or voltage
at specified current as
Solvent temperature:
specified in the detail
23°C
specification
Conditioning method 2
Recovery time: 48 h
Rapid change of 6.20 upper category Visual inspection:
temperature temperature No visual damage
ϑ = UCT Leakage current or voltage
sup
at specified current as
lower category
specified in the detail
temperature
specification
ϑ = LCT
inf
– 18 – IEC 61051-2:2021 © IEC 2021
a a a
Sample Test Subclause Conditions of test Performance
D or n c
Group of a requirements
ND
No. 61051‑1:2018
Group 5B D 8 0
Other half of the
samples of group 5
b)
6.21 IEC 60068-2-27, Test Ea Visual inspection:
Shock
No visual damage
Pulse shape: half-sine
Leakage current or voltage
A = 500 m/s
at specified current as
specified in the detail
D = 11 ms
specification
N = 6 × 3 shocks
b)
6.21 IEC 60068-2-27, Test Ea Visual inspection:
Repetitive shock
No visual damage
Pulse shape: half sine.
Leakage current or voltage
A = 400 m/s
at specified current as
specified in the detail
D = 6 ms
specification
N = 6 × 5 000 shocks
Vibration 6.22 IEC 60068-2-6, Test Fc, Visual inspection:
Method B4 No visual damage
Frequency range: 10 Hz Leakage current or voltage
to 55 Hz at specified current as
specified in the detail
A = 0,75 mm or 98 m/s
specification
(whichever is the less)
D = 3 × 2 h
Combined sample of D 16 0
specimens of
Sub‑groups 5A and 5B
Climatic sequence 6.23
– Dry heat IEC 60068-2-2, Test Bb Visual inspection:
(16 ± 2) h, No visual damage and the
marking shall be legible
T = UCT ± 2 °C
Leakage current or voltage
– Damp heat, cyclic, IEC 60068-2-30, Test Db
at specified current as
Test Db, first cycle 24h, T = (55 ± 2) °C

specified in the detail
– Cold IEC 60068-2-1, Test Ab
specification
2h, T = LCT ± 3 °C
Insulation resistance as
– Damp heat, cyclic, IEC 60068-2-30, Test Db
specified in the detailed
Test Db, remaining
24h, T = (55 ± 2) °C;
specification
cycles
– Final measurement
Group 6
6 D 8 0
Endurance at upper 6.26 Examination at 48, 500 and
T = UCT ± 2°C,
category temperature 1 000 h:
Duration: 1 000 h
Visual inspection:
Voltage: max. continuous
No visual damage
AC or DC voltage
Voltage at specified
current as specified in the
detail specification
Additional Examination at
1 000 h:
Clamping Voltage at class
current as specified in the
detail specification
Insulation resistance as
specified in the detailed
specification (Insulated
varistors only)
Fire hazard (Needle 6.25 IEC 60695-11-5 Duration of burning:
flame test) Severity: Vertical 10 s 5 s maximum
a
D: Destructive test
ND: Non-destructive test
n: Number of specimens to be tested
c: Permissible numbers of non-conforming items
b
Shock and repetitive shock test are considered to be alternative. The detail specification indicate which test is
performed.
8.5 Quality conformance inspection
8.5.1 General
Blank detail specifications IEC 61051-2-2 associated with this specification shall
...