SIST EN IEC 61051-2:2022

Varistors for use in electronic equipment - Part 2: Sectional specification for surge suppression varistors (IEC 61051-2:2021)

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. Test severities and requirements prescribed in detail specifications referring to this sectional specification should be of equal or higher performance level, because lower performance levels are not permitted.

Varistoren zur Verwendung in Geräten der Elektronik – Teil 2: Rahmenspezifikation für Varistoren für den Überspannungsschutz (IEC 61051-2:2021)

Varistances utilisées dans les équipements électroniques - Partie 2: Spécification intermédiaire pour varistances pour limitations de surtensions transitoires (IEC 61051-2:2021)

L’IEC 61051-2:2021 est une spécification intermédiaire applicable aux varistances à oxyde métallique présentant des caractéristiques de tension-courant symétriques, destinées à être utilisées dans les équipements électroniques reliés à un système d’alimentation en courant alternatif ou continu.
Ces varistances sont conçues pour protéger les équipements électroniques et autres équipements sensibles contre les surtensions transitoires. Les varistances relevant du domaine d’application de la présente spécification intermédiaire ne sont pas destinées à assurer la protection primaire contre la foudre.
Ces varistances disposent de connexions métalliques et sont destinées à être montées en tant que composant à trous traversants ou directement sur les cartes imprimées.
Le présent document a pour but de prescrire les caractéristiques assignées et les caractéristiques préférentielles, de choisir dans l’IEC 61051-1 les procédures d’assurance de la qualité et les méthodes d’essai et de mesure appropriées, et de fixer les exigences de performance générales pour ce type de varistances.
Cette édition inclut les modifications techniques majeures suivantes par rapport à l’édition précédente:
a) révision de la structure conformément aux Directives ISO/IEC, Partie 2, dans la mesure du possible, et harmonisation avec l’IEC 61051-1:2018;
b) ajout de l’Annexe X à des fins de comparaison avec l’édition précédente;
c) ajout de deux listes de caractéristiques assignées de tension préférentielles pour les varistances de type disque et de type CMS;
d) nombre admissible d’éléments non conformes fixé à zéro (zéro défaut) dans le programme d’essai en 8.4.3.

Varistorji za elektronsko opremo - 2. del: Področna specifikacija za varistorske prenapetostne odvodnike (IEC 61051-2:2021)

Ta del standarda IEC 61051 je področna specifikacija in se uporablja za kovinsko-oksidne varistorje s simetričnimi značilnostmi napetostnega toka za uporabo v elektronski opremi, ki je priključena na kateri koli enosmerni ali izmenični napajalni sistem.
Ti varistorji so zasnovani za zaščito elektronske in druge občutljive opreme pred visoko prehodno prenapetostjo. Varistorji, ki spadajo na področje uporabe te področne specifikacije, ne zagotavljajo primarne zaščite pred udari strele.
Ti varistorji imajo kovinske povezave in so namenjeni za namestitev kot vtična komponenta ali neposredno na tiskano vezje.
Cilj tega dokumenta je predpisati prednostne vrednosti in lastnosti, izbrati primerne postopke za ovrednotenje kakovosti, preskuse in merilne metode iz standarda IEC 61051-1 ter podati splošne zahteve glede zmogljivosti za ta tip varistorjev. Preskusne stopnje in zahteve, predpisane v podrobnih specifikacijah, ki se navezujejo na to področno specifikacijo, morajo biti enake ali višje ravni učinkovitosti, kajti nižje ravni niso dovoljene.

General Information

• Status: Published
• Publication Date: 09-Jan-2022
• ICS: 31.040.20 - Potentiometers, variable resistors
• Technical Committee: I11 - Imaginarni 11
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 24-Dec-2021
• Due Date: 28-Feb-2022
• Completion Date: 10-Jan-2022
• Ref Project: EN IEC 61051-2:2021 - Varistors for use in electronic equipment - Part 2: Sectional specification for surge suppression varistors

Standards Content (Sample)

SLOVENSKI STANDARD
SIST EN IEC 61051-2:2022
01-februar-2022
Varistorji za elektronsko opremo - 2. del: Področna specifikacija za varistorske
prenapetostne odvodnike (IEC 61051-2:2021)
Varistors for use in electronic equipment - Part 2: Sectional specification for surge
suppression varistors (IEC 61051-2:2021)
Varistoren zur Verwendung in Geräten der Elektronik – Teil 2: Rahmenspezifikation für
Varistoren für den Überspannungsschutz (IEC 61051-2:2021)
Varistances utilisées dans les équipements électroniques - Partie 2: Spécification
intermédiaire pour varistances pour limitations de surtensions transitoires (IEC 61051-
2:2021)
Ta slovenski standard je istoveten z: EN IEC 61051-2:2021
ICS:
31.040.20 Potenciometri, spremenljivi Potentiometers, variable
upori resistors
SIST EN IEC 61051-2:2022 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------
SIST EN IEC 61051-2:2022

---------------------- Page: 2 ----------------------
SIST EN IEC 61051-2:2022


EUROPEAN STANDARD EN IEC 61051-2

NORME EUROPÉENNE

EUROPÄISCHE NORM
December 2021
ICS 31.040.20

English Version
Varistors for use in electronic equipment - Part 2: Sectional
specification for surge suppression varistors
(IEC 61051-2:2021)
Varistances utilisées dans les équipements électroniques - Varistoren zur Verwendung in Geräten der Elektronik - Teil
Partie 2: Spécification intermédiaire pour varistances pour 2: Rahmenspezifikation für Varistoren für den
limitations de surtensions transitoires Überspannungsschutz
(IEC 61051-2:2021) (IEC 61051-2:2021)
This European Standard was approved by CENELEC on 2021-12-13. 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, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the
Netherlands, Norway, Poland, Portugal, Republic of North Macedonia, 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
© 2021 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
 Ref. No. EN IEC 61051-2:2021 E

---------------------- Page: 3 ----------------------
SIST EN IEC 61051-2:2022
EN IEC 61051-2:2021 (E)
European foreword
The text of document 40/2877/FDIS, future edition 2 of IEC 61051-2, prepared by IEC/TC 40
“Capacitors and resistors for electronic equipment” was submitted to the IEC-CENELEC parallel vote
and approved by CENELEC as EN IEC 61051-2:2021.
The following dates are fixed:
• latest date by which the document has to be implemented at national (dop) 2022–09–13
level by publication of an identical national standard or by endorsement
• latest date by which the national standards conflicting with the (dow) 2024–12–13
document have to be withdrawn
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.
Any feedback and questions on this document should be directed to the users’ national committee. A
complete listing of these bodies can be found on the CENELEC website.
Endorsement notice
The text of the International Standard IEC 61051-2:2021 was approved by CENELEC as a European
Standard without any modification.
2

---------------------- Page: 4 ----------------------
SIST EN IEC 61051-2:2022
EN IEC 61051-2:2021 (E)
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 60062 - Marking codes for resistors and capacitors EN 60062 -
IEC 60068-1 - Environmental testing - Part 1: General EN 60068-1 -
and guidance
IEC 60068-2-1 - Environmental testing - Part 2–1: Tests - EN 60068-2-1 -
Test A: Cold
IEC 60068-2-2 - Environmental testing - Part 2–2: Tests - EN 60068-2-2 -
Test B: Dry heat
IEC 60068-2-6 - Environmental testing - Part 2–6: Tests - EN 60068-2-6 -
Test Fc: Vibration (sinusoidal)
IEC 60068-2-20 - Environmental testing - Part 2–20: Tests - EN IEC 60068-2-20 -
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 - EN 60068-2-27 -
Test Ea and guidance: Shock
IEC 60068-2-30 - Environmental testing - Part 2–30: Tests - EN 60068-2-30 -
Test Db: Damp heat, cyclic (12 h + 12 h
cycle)
IEC 60068-2-45 - Basic environmental testing procedures - EN 60068-2-45 -
Part 2–45: Tests - Test XA and guidance:
Immersion in cleaning solvents
IEC 60695-11-5 - Fire hazard testing - Part 11–5: Test EN 60695-11-5 -
flames - Needle-flame test method -
Apparatus, confirmatory test arrangement
and guidance
IEC 61051-1 2018 Varistors for use in electronic equipment - EN IEC 61051-1 2018
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
3

---------------------- Page: 5 ----------------------
SIST EN IEC 61051-2:2022
EN IEC 61051-2:2021 (E)
IEC 61193-2 2007 Quality assessment systems - Part 2: EN 61193-2 2007
Selection and use of sampling plans for
inspection of electronic components and
packages


4

---------------------- Page: 6 ----------------------
SIST EN IEC 61051-2:2022




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




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

---------------------- Page: 7 ----------------------
SIST EN IEC 61051-2:2022
– 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

---------------------- Page: 8 ----------------------
SIST EN IEC 61051-2:2022
IEC 61051-2:2021 © IEC 2021 – 3 –
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

---------------------- Page: 9 ----------------------
SIST EN IEC 61051-2:2022
– 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.

---------------------- Page: 10 ----------------------
SIST EN IEC 61051-2:2022
IEC 61051-2:2021 © IEC 2021 – 5 –
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.

---------------------- Page: 11 ----------------------
SIST EN IEC 61051-2:2022
– 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

---------------------- Page: 12 ----------------------
SIST EN IEC 61051-2:2022
IEC 61051-2:2021 © IEC 2021 – 7 –
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.

---------------------- Page: 13 ----------------------
SIST EN IEC 61051-2:2022
– 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

---------------------- Page: 14 ----------------------
SIST EN IEC 61051-2:2022
IEC 61051-2:2021 © IEC 2021 – 9 –
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.

---------------------- Page: 15 ----------------------
SIST EN IEC 61051-2:2022
– 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

---------------------- Page: 16 ----------------------
SIST EN IEC 61051-2:2022
IEC 61051-2:2021 © IEC 2021 – 11 –
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
...