IEC 61811-10:2002

IEC 61811-10 ®
Edition 1.0 2002-11
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Electromechanical elementary relays of assessed quality –
Part 10: Sectional specification – Relays for industrial application

Relais électromécaniques élémentaires sous assurance de la qualité –
Partie 10: Spécification intermédiaire – Relais pour applications industrielles

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IEC 61811-10 ®
Edition 1.0 2002-11
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Electromechanical elementary relays of assessed quality –

Part 10: Sectional specification – Relays for industrial application

Relais électromécaniques élémentaires sous assurance de la qualité –

Partie 10: Spécification intermédiaire – Relais pour applications industrielles

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
CODE PRIX S
ICS 29.120.70 ISBN 978-2-8322-1323-0

– 2 – 61811-10  IEC:2002
CONTENTS
FOREWORD . 3

1 General . 5
1.1 Scope . 5
1.2 Normative references . 5
1.3 Marking . 6
1.4 Ordering information . 6
2 Quality assessment procedures . 6
2.1 Primary stage of manufacture . 6
2.2 Structurally similar relays . 6
2.3 Subcontracting . 7
2.4 Qualification approval procedures . 7
2.5 Quality conformance inspection requirements. 7
2.6 Test schedule . 7
2.7 Order of tests . 8
3 Preparation of blank detail and detail specifications . 8
3.1 Contents of blank detail and detail specifications. 8
3.2 Basic test schedule . 9
3.3 Test schedule for blank detail specifications . 10
4 Relay reliability – Failure rate data . 13

Annex A (informative) Explanations and examples regarding IL and AQL values . 15
Annex B (informative) Data base for failure rates . 17

Figure B.1 – Factor π depending on the operating cycles . 20
S
Table 1 – Tests for quality conformance inspection . 10-13
Table B.1 – Factor π . 20
ES
Table B.2 – Factor π . 21
T
61811-10  IEC:2002 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ELECTROMECHANICAL ELEMENTARY RELAYS
OF ASSESSED QUALITY –
Part 10: Sectional specification –
Relays for industrial application

FOREWORD
1) The IEC (International Electrotechnical Commission) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of the 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, the IEC publishes International Standards. 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. The 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 the 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 National Committees.
3) The documents produced have the form of recommendations for international use and are published in the form
of standards, technical specifications, technical reports or guides and they are accepted by the National
Committees in that sense.
4) In order to promote international unification, IEC National Committees undertake to apply IEC International
Standards transparently to the maximum extent possible in their national and regional standards. Any
divergence between the IEC Standard and the corresponding national or regional standard shall be clearly
indicated in the latter.
5) The IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with one of its standards.
6) Attention is drawn to the possibility that some of the elements of this International Standard may be the subject
of patent rights. The IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 61811-10 has been prepared by IEC technical committee 94: All-
or-nothing electrical relays.
This standard cancels and replaces IEC 60255-19 (1983) and constitutes a technical revision.
This bilingual version (2014-01) corresponds to the monolingual English version, published in
2002-11.
The text of this standard is based on the following documents:
FDIS Report on voting
94/168/FDIS 94/172/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
The French version of this standard has not been voted upon.
The QC number that appears on the front cover of this publication is the specification number
in the IEC Quality Assessment System for Electronic Components (IECQ).
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.

– 4 – 61811-10  IEC:2002
The committee has decided that the contents of this publication will remain unchanged until
2006. At this date, the publication will be
• reconfirmed;
• withdrawn;
• replaced by a revised edition, or
• amended.
61811-10  IEC:2002 – 5 –
ELECTROMECHANICAL ELEMENTARY RELAYS
OF ASSESSED QUALITY –
Part 10: Sectional specification –
Relays for industrial application

1 General
1.1 Scope
This part of IEC 61811 is a sectional specification applicable to electromechanical elementary
(non-specified time all-or-nothing) relays of assessed quality for industrial application.
NOTE Electromechanical all-or-nothing telecom relays of assessed quality are covered by IEC 61811-50.
It is based on the basic relay standard IEC 61810-1 as well as on the generic specification
IEC 61811-1 and selects from IEC 61810-7 the appropriate test and measurement procedures
to be used in detail specifications derived from this specification. Moreover it contains a basic
test schedule to be used in the preparation of such specifications. Detailed test schedules are
given in the blank detail specifications supplementary to this sectional specification.
For the purpose of this standard, only fundamental tests have been compiled. Depending on
the field of application, further tests should be selected as appropriate, preferably in
accordance with the test and measurement procedures of IEC 61810-7.
1.2 Normative references
The following referenced documents are indispensable for the application of this document.
For dated references, only the edition cited applies. For undated references, the latest edition
of the referenced document (including any amendments) applies.
IEC 60062:1992, Marking codes for resistors and capacitors
IEC 60255-23:1994, Electrical relays – Part 23: Contact performance
IEC 60410:1973, Sampling plans and procedures for inspection by attributes
IEC 61709:1996, Electronic components – Reliability – Reference conditions for failure rates
and stress models for conversion
IEC 61810-1:1998, Electromechanical non-specified time all-or-nothing relays – Part 1:
General requirements
IEC 61810-5:1998, Electromechanical non-specified time all-or-nothing relays – Part 5:
Insulation coordination
IEC 61810-7:1997, Electromechanical all-or-nothing relays – Part 7: Test and measurement
procedures
IEC 61811-1:1999, Electromechanical non-specified time all-or-nothing relays of assessed
quality – Part 1: Generic specification
IEC QC 001002-3, IEC Quality Assessment System for Electronic Components (IECQ) –
Rules of Procedure – Part 3: Approval procedures

– 6 – 61811-10  IEC:2002
1.3 Marking
Relays and their package supplied in accordance with detail specifications covered by this
sectional specification, shall as a minimum be marked as follows:
1.3.1 Relay
• Trade mark or manufacturer’s name
• Relay type and variant code
• Date of manufacture, year/week, coded in accordance with IEC 60062
• IECQ mark
Where space permits, a circuit diagram or terminal identification should be given.
1.3.2 Package
• Trade mark or manufacturer’s name
• Detail specification reference if not marked on the relay
• Quantity
• Relay type and variant code
• Manufacturer’s batch identification code
1.4 Ordering information
The ordering information shall be coded and shall contain the following details:
• IECQ detail specification number
• Coded coil voltage
• Terminal code
• Coded mounting arrangement
• Specials code
2 Quality assessment procedures
2.1 Primary stage of manufacture
The primary stage of manufacture is the first process subsequent to the manufacture of
finished parts and subassemblies of the relay.
NOTE 1 A subassembly is understood to mean here the permanent assembly of two or more piece parts.
NOTE 2 Important manufacturing steps are as follows:
a) fabrication, heat treatment and plating of the component parts of the relay;
b) coil winding;
c) assembling of the electrical and electromechanical parts;
d) adjustment of the relay contacts, if applicable;
e) high-temperature drying, gas backfilling and sealing of the relay, if applicable;
f) final measurements and periodic inspection of test groups A to D.
2.2 Structurally similar relays
Relays are considered structurally similar if having no differences in design other than in:
a) coil wire diameter, number of windings and the coil transient suppression device;
b) types, numbers and material of contacts;
c) rated coil and/or contact voltage(s);
d) mounting and terminal variants within the limits prescribed in the detail specification.

61811-10  IEC:2002 – 7 –
2.3 Subcontracting
Subcontracting the primary stage of manufacture (see 2.1) and/or subsequent stages to an
unapproved manufacturer is forbidden. Subcontracting is permitted for any stages preceding
the primary stage of manufacture and shall be in accordance with the requirements of
(normative) Annex B to Clause 2 of IEC QC 001002-3.
2.4 Qualification approval procedures
The manufacturer shall comply with the general requirements of the basic rules governing
qualification approval defined in Clause 3 of IEC QC 001002-3 and the provisions given in 2.2
of IEC 61811-1.
The requirements contained in 4.2 of IEC 61810-1 shall be met.
Qualification approval tests shall include all the tests prescribed in the detail specification,
and shall be performed by a schedule specifically prescribed in the detail specification.
Sampling shall be carried out in accordance with the sampling plans and procedures specified
in IEC 60410. The number of specimens for each subgroup is specified in the blank detail
specification. As a general rule, a minimum of five specimens are required for each group of
tests. The qualification tests schedule may specify destructive and cumulative non-destructive
tests.
2.5 Quality conformance inspection requirements
2.5.1 General requirements
Quality conformance inspection shall be carried out in accordance with the requirements of
Clause 3 of IEC QC 001002-3 and 2.3 of IEC 61811-1.
2.5.2 Formation of inspection lots
Inspection lots to be submitted to group A and B acceptance tests shall be formed in
accordance with 3.2.3 and 3.3.1 of IEC QC 001002-3 and with the sampling plans and
procedures given in IEC 60410, except where production is too infrequent or too small for
sampling plans to apply; in these cases inspection shall be 100 %.
When sampling is carried out in accordance with IEC 60410, the percent defective concept
only shall be used. Stratified or representative sampling shall always be used to include all
production lines and structurally similar relays in proportion to their respective quantities in
the lot. Exceptions from proportionality may become necessary and shall be stated in the
detail specification or agreed between the manufacturer and the National Supervising
Inspectorate (NSI). Specimens shall be as representative as possible of the production.
2.5.3 Periodic inspection
Fixed samples for group C and D inspection shall be taken from a lot (or lots) which has
passed group A and B inspection during, or at the end, of the specified reference period. In
both cases the inspection lot (or lots) shall not be less than the average of production lots
during the reference period for each group.
2.6 Test schedule
2.6.1 Test sequence
A test sequence shall consist of all tests listed in the (blank) detail specification.
The reference numbers of the tests are those of IEC 61810-7, with the exception of additional
test(s) described in the sectional, the blank detail or the detail specification.

– 8 – 61811-10  IEC:2002
2.6.2 Groups A and B
The IL (inspection level) notation applies for all tests in one subgroup. A corresponding range
of values for AQL (acceptable quality level) shall be given in the blank detail specification,
and the authority preparing detail specifications shall choose the appropriate value which then
applies to all tests in one subgroup.
2.6.3 Groups C and D
The blank detail specification shall prescribe for each subgroup:
a) Periodicity of this subgroup. If the same periodicity is applicable to all subgroups, it shall
be given at the beginning of the group test details.
b) The minimum sample size for each test (or group of tests) performed with the same
relays, the number of test specimens and the permitted number of defectives shall be
specified.
2.7 Order of tests
Quality conformance inspection is divided into two parts: that carried out lot-by-lot, on which
the release of the individual lots is based, and that carried out on a periodic basis which
contains the time-consuming and more expensive tests.
Following 2.3 of IEC 61811-1, groups A and B contain lot-by-lot tests, while periodic tests
required for the maintenance of qualification approval are contained in groups C and D.
When several tests are subsequently to be carried out on any one specimen or number of
specimens, the following order shall apply unless otherwise prescribed in the blank detail
specification:
– Screening or sorting tests (if applicable) and subgroup A1 shall always precede any other
non-destructive (ND) or destructive (D) tests.
– The remaining tests shall be conducted as given in the blank detail specification. The
order of tests within subgroups is mandatory.
– Destructive tests may be preceded by one or more non-destructive or destructive tests,
provided that the effects of the preceding tests are not considered liable to invalidate the
results of the later tests.
3 Preparation of blank detail and detail specifications
3.1 Contents of blank detail and detail specifications
Blank detail specifications shall conform with the test schedule given in Table 1 of this
specification and the related explanations.
Tests marked M are mandatory. If tests are marked R (recommended) they may be included
in the blank detail specification; they then become mandatory for the detail specification.
Blank detail specifications shall give the following information or call for inclusion into the
detail specification:
a) Identification of the detail specification.
b) Identification of the relay and information on its applications. Identification shall be
provided by such properties as rated power, dimensions, sealing, whether monostable or
bistable, polarised or not, or otherwise required for identification.
c) Outline drawings of the relay and key dimensions. Variants, such as for terminals, may be
given in an annex to the detail specification.

61811-10  IEC:2002 – 9 –
d) Reference data of the relay. A limited number of values is required on the front page, so
as to describe the overall performance of the relay. Full information in conformance with
IEC 61810-1 shall be added on one of the subsequent pages. Rated values should
preferably be those listed therein. Where tests are referred to rated values, they shall be
indicated with each test. Where tests are to be performed at other than rated values, the
test values shall be indicated and clearly distinguished from the rated values.
e) Related documents. Reference shall be made to IEC 61811-1 and this sectional
specification. When reference to further documents is necessary, such documents shall be
listed with their full title, year of edition and, unless common knowledge, the source from
which they can be obtained.
f) Periodicity of tests.
g) Formation of inspection lots, if predictable in the sense of 2.5.
h) Order of the tests.
i) General test conditions, if deviating from 3.5 of IEC 61810-7.
j) Qualification approval test schedule.
k) Quality conformance test schedule.
l) Specification of IL numbers (groups A and B) and sample sizes (groups C and D).
m) Specification of AQL numbers (groups A and B) and permitted number of defectives
(groups C and D).
n) Marking of package and/or relays, ordering information beyond that listed in this
specification, if necessary.
o) Coded ordering information.
Additional information such as curves and drawings may be given in an annex of the detail
specification.
When preparing blank detail specifications, the following steps are to be taken:
– include in the blank detail specification all the mandatory tests of Table 1, together with
those recommended tests considered appropriate for the intended use;
– if necessary, add any other tests required either from or beyond IEC 61810-7.
3.2 Basic test schedule
The basic test schedule is given in Table 1.
3.2.1 Order of tests
The order within subgroups shall be defined in the blank detail specification.
3.2.2 Sampling values
IL and AQL values, sample size and allowed defectives shall be chosen from IEC 60410 and
by using Annex A, and shall be stated in the blank detail specification.
3.2.3 Abbreviations
Options:
Tests marked with M are mandatory for inclusion in the (blank) detail specification.
Tests marked with R are recommended for inclusion in the (blank) detail specification.

– 10 – 61811-10  IEC:2002
Types of relays:
RT 0 Unenclosed relay
RT I Dust protected relay
RT II Flux proof relay
RT III Wash tight relay
RT IV Sealed relay
RT V Hermetically sealed relay
The respective definitions are given in 2.2 of IEC 61810-7.
3.3 Test schedule for blank detail specifications
The mandatory and recommended tests for quality conformance inspection to be used for the
establishment of a test schedule in a blank detail specification are given in Table 1 below.
Table 1 – Tests for quality conformance inspection
Group A
Conducted on a sampling basis, lot by lot.
Subgroup A1
For all tests in this subgroup IL: .
AQL: .
Test from IEC 61810-7
Options and particular requirements
and respective subclause number
Visual inspection – relay marking (ND) M
3.6.4 items a) and b)
Coil resistance (ND) M
3.8.1
Dielectric test (ND) M In accordance with Clauses 3 and 4 of
3.9 IEC 61810-5
Contact-circuit resistance, static (ND) M Test voltage and current according to
3.12 CA category/ies specified for the relay
Functional tests (ND) M Operate and release value shall be
3.13 checked as a minimum. In accordance
with 4.1.2 of IEC 61810-1
Timing tests (ND) R
3.14.2
61811-10  IEC:2002 – 11 –
Group B
Conducted on a sampling basis, lot by lot.
Subgroup B2
For all tests in this subgroup IL: .
AQL: .
Test from IEC 61810-7
Options and particular requirements
and respective subclause number
Visual inspection other than marking (ND) M For the relay
3.6.4 items c) and d) R For accessories and packaging, as applicable
Check of dimensions (ND) M For key dimensions
3.6.1
R For all other dimensions, including clearances
and creepage distances
Group C
Periodic tests with fixed sample size
Subgroup C1
Periodicity: . months
Sample size: . specimens
Test from IEC 61810-7
Options and particular requirements
and respective subclause number
Heating (ND) M In accordance with 4.1.6 of IEC 61810-1
3.18
Dielectric test (ND) M In accordance with Clauses 3 and 4 of IEC 61810-5
3.9
Impulse voltage test (ND) M In accordance with Clause 4 of IEC 61810-5
3.10
Insulation resistance (ND) M
3.11
Enclosure (ND) R
3.20
Subgroup C2
Periodicity: . months
Sample size: . specimens
Test from IEC 61810-7
Options and particular requirements
and respective subclause number
Electrical endurance (D) M In accordance with the provisions of
3.30 IEC 60255-23 and 4.1.5 of IEC 61810-1

– 12 – 61811-10  IEC:2002
Subgroup C3
Periodicity: . months
Sample size: . specimens
Test from IEC 61810-7
Options and particular requirements
and respective subclause number
Timing tests (ND) M Only if not tested in subgroup A1
3.14
Coil transient suppression (ND) R For relays with transient suppression device only
3.8.4
Weighing (ND) R
3.7.2
Check of dimensions (ND)/(D) M For all dimensions including clearances and
3.6.1 creepage distances, if not tested in subgroup B2

Subgroup C5
Periodicity: . months
Sample size: . specimens
Test from IEC 61810-7
Options and particular requirements
and respective subclause number
Rapid change of temperature (D) R Sealed relays (RT IV and RT V) only
3.19
Resistance to soldering heat (D) M For relays with solder terminals only
3.25
Climatic sequence (D) R
3.15
Damp heat, steady state (D) R
3.16
Robustness of terminals (D) R For QC (quick-connect) terminals only:
3.24 according to 4.1.9 of IEC 61810-1.
Shock (D) R
3.26
Bump (D) R
3.27
Vibration (D) R
3.28
Mechanical endurance (D) R In accordance with 4.1.4 of IEC 61810-1
3.31
Thermal endurance (D) R
3.32
Fire hazard (D) M In accordance with 4.1.7 of IEC 61810-1
3.48
61811-10  IEC:2002 – 13 –
Subgroup C6
Periodicity: . months
Sample size: . specimens
Test from IEC 61810-7
Options and particular requirements
and respective subclause number
Resistance to cleaning solvents (ND) R
3.47.2
Electrical contact noise (ND) R Only if required
3.39
Mould growth (D) R Only if required
3.23
Corrosive atmospheres (D) R Only if required
3.22
Group D
Periodicity: . months
Sample size: . specimens
Test from IEC 61810-7
Options and particular requirements
and respective subclause number
Coil impedance (ND) R For a.c. relays only
3.8.3
Internal moisture (ND) R Only if applicable
3.21
Solderability (D) M For relays with solder terminals only
3.25
4 Relay reliability – failure rate data
The evaluation and indication of reliability data is not mandatory.
However, if required in a detail specification, the failure rate data for the reliability prediction
of relays in electronic equipment shall be stated in an appropriate way. It is strongly
recommended to give such data in accordance with IEC 61709. Therefore, the preferred
(blank) data base for failure rates, the stress model and the particular stress factors for
conversion of the failure rate data at reference conditions to the actual operating conditions
are given in informative Annex B. In the relevant detail specification, reference shall be made
to this Annex B and further details be given.
The reference failure rate shall be determined by the manufacturer for his particular relay
type. The relay manufacturer is required to log cumulatively all endurance test data and all
other relevant data including those derived from field experience, which would demonstrate/
indicate achieved reliability. The endurance tests specified in the detail specification are
intended, amongst other things, to provide a measure of the failure rate under prescribed
conditions.
– 14 – 61811-10  IEC:2002
If another stress model, or other stress factors respectively, are known to be more suitable for
a particular relay type, such deviations shall be clearly described in an Annex of the relevant
detail specification and used instead (all necessary details which allow the conversion of the
failure rate data to the actual operating conditions and the source(s) of these data shall be
described). However, the statements in B.8 shall be kept in this case.
All the activities listed above shall be performed under the supervision of the National
Supervising Inspectorate (NSI).
NOTE Relay manufacturers are not required to demonstrate the achievement of the failure rate data before
delivery of a specific lot.
61811-10  IEC:2002 – 15 –
Annex A
(informative)
Explanations and examples regarding IL and AQL values

A.1 Introduction
This sectional specification refers to, and detail specifications derived from it will generally
use, the concept of IEC 60410 which is based on notations called IL and AQL values.
This informative annex explains in a rather simple form the meaning of inspection level (IL)
and acceptable quality level (AQL) while showing by some examples the consequences from
choosing IL and AQL values.
It is not intended to replace or supersede the far more detailed terminology and specifications
contained in IEC 60410.
A.2 Inspection level (IL)
The inspection level determines the relationship between the lot or batch size and the sample
size. This relationship is established by means of a table in IEC 60410 which contains lines
for various lot or batch sizes, from 2 to more than 50 000, and contains columns for seven
different inspection levels. These levels are divided into two groups.
The general inspection levels are I, II and III from which IL II is normally used, while IL I
results in a smaller, and IL III in a larger number of test specimens.
The special inspection levels are S-1 to S-4 and result in far smaller sample sizes. They are
to be used for expensive tests, for example destructive tests or tests of long duration. IL S-1
results in the smallest, and IL S-4 results in the largest sample size among the special
inspection levels.
A.3 Sample sizes versus IL values
If single sampling and normal inspection (see IEC 60410 for the explanations of these terms)
are used, the following examples of relationship between lot or batch size and sample size
apply.
Sample size for IL
Lot or batch size
S-1 S-2 S-3 S-4 I II III
91 to 150 3 3 5 8 8 20 32
501 to 1 200 5 5 13 20 32 80 125
10 001 to 35 000 5 8 20 50 125 315 500

– 16 – 61811-10  IEC:2002
A.4 Acceptable quality level (AQL)
The acceptable quality level is – simply explained – the percentage of defectives within a lot
which a buyer is willing to admit, and which is ensured to him, by means of sampling
inspection, at given probability. This probability is of the order of 90 % but varies with the
chosen IL and AQL.
The AQL is the index of tables in IEC 60410 which relate two figures to a given AQL and the
sample sizes determined as above: the figure Ac (accepted) is the maximum of defectives up
to which the lot or batch is accepted. The figure Re (rejected) is the number of defectives
above which the lot or batch is rejected.
A.5 Admitted defectives versus AQL
If single sampling, normal inspection and IL II are used, the following examples of relationship
between sample size and number of allowed defectives apply.
It is to be noted that some AQL values may require a larger or smaller sample size than
determined in accordance with the IL value. This is indicated by arrows in the following table:
Number of allowed defectives (Ac) at IL II and AQL
Sample
Lot size
size
0,25 0,40 0,65 1,0 1,5 2,5
⇑
91-150 20 use 50 use 32 0 use 13 use 32 1
specimens specimens specimens specimens

⇓ ⇓ ⇓
0 0  1
⇑
501-1 200 80 use 50 use 125 1 2 3 5
specimens specimens
⇓
10 001-
35 000 315 2 3 5 7 10 14
61811-10  IEC:2002 – 17 –
Annex B
(informative)
Data base for failure rates
B.1 Scope
This annex details the data base for failure rates of relays based on IEC 61709. If required in
the relevant (blank) detail specification, the information given below and any further details
necessary should be given in a respective annex in that specification.
B.2 Description of the relay
B.2.1 Identification
The XY relay is [details to be given in the detail specification]. For further details, see
boxes (5) and (6) under 1.3 of the relevant (blank) detail specification.
NOTE Numbering of the boxes in brackets in this annex corresponds to the front page layout given under 1.3 of
the relevant (blank) detail specification.
B.2.2 Ratings
Coil data and contact data, see boxes (9), (10) and (11) under 1.3 of the relevant (blank)
detail specification.
B.3 Quality level
B.3.1 Form of qualification:
IECQ qualification approval and quality conformance inspections according to Clauses 3
and 4 of the relevant (blank) detail specification.
B.4 Fault and failure data
B.4.1 Fault definition
According to 2.25, 2.26 and 2.28 of IEC 60255-23 – see also B.4.3.
B.4.2 Fault application
Useful life time period. Beginning of useful life time: relay in new condition; end of useful life
time: number of switching cycles stated in the relevant (blank) detail specification.
B.4.3 Failure definition
According to 2.27, 2.28, 2.29 and 2.30 of IEC 60255-23.
B.4.4 Failure application
Wear-out failure time period.
NOTE For conversion of the cycle-related to the time-related failure rate, see E.2.4 of IEC 60255-23.

– 18 – 61811-10  IEC:2002
B.5 Source of data
B.5.1 Failure rate under reference conditions, λ specified in B.7
ref
Manufacturer’s laboratory tests in accordance with 5.2.1.2 of IEC 60255-23.
B.5.2 Stress factors π , π and π
ES S T
According to 7.7 of IEC 61709 – see B.10.
B.5.3 Data level
Single relay.
B.6 Conditions for which failure rates apply
The application of the failure rates described in this annex is limited by the following values
stated in the relevant (blank) detail specification:
– ratings – see boxes (9) and (10) under 1.3
– component climatic category according to IEC 60068 – see box (11) under 1.3
– operating range – see box (11) under 1.3
– environmental data – see 2.7.
B.7 Reference failure rate λ
ref
B.7.1 The failure rate under reference conditions specified in B.7.2 to B.7.7:
λ = . per operating cycle
ref
B.7.2 Factors for failure rate under reference conditions
B.7.2.1 Time period
Mean failure rate related to wear-out time period according to C.3 of IEC 60255-23 (µ value)
with confidence level of 90 %.
B.7.2.2 Failure criterion
Fault and failure definitions according to B.4.
B.7.2.3 Operating mode
Accelerated conditions in accordance with E.1 of IEC 60255-23 simulating one operating
cycle per hour.
B.7.2.4 Climatic and mechanical stresses
Ambient temperature: 40 °C
Climatic conditions: 3K3 of IEC 60721-3-3
Mechanical stresses: 3K3 of IEC 60721-3-3

B.7.2.5 Electrical stresses
Stress region 2 according to Figure 9 of IEC 61709: 0,5 V < U ≤ U , 0 A < I ≤ 0,1 A.
rat
61811-10  IEC:2002 – 19 –
B.7.2.6 Supplementary statements
No supplementary statements required.
B.8 Methods for combining and adding new data
The relay manufacturer should log cumulatively all endurance test data and all other relevant
data including that ones derived from field experience which would demonstrate / indicate
achieved reliability. All endurance tests specified in the relevant (blank) detail specification
are intended, amongst other things, to provide a measure of the failure rate under prescribed
conditions.
The relay manufacturer should check systematically the validity of the failure rate data by a
particular communication/co-operation with the relevant relay user(s). The relay manufacturer
should keep the necessary records on this matter and suggest amendments (particularly of
Clause B.10) if necessary.
All these activities should be performed under the supervision of the National Supervising
Inspectorate (NSI).
B.9 Stress model
The following stress model and stress factors should be used for conversion of the failure rate
at reference conditions (λ ) to the failure rate under actual operating conditions (λ). This
ref
conversion is only permissible within the functional limits specified in the relevant (blank)
detail specification and in connection with the statements in IEC 61709.
The failure rate under operating conditions is calculated as follows:
λ = λ × π × π × π
ref ES S T
where
λ failure rate under operating conditions
λ failure rate under reference conditions – see B.7
ref
π electrical stress dependence factor – see Table B.1
ES
π switching rate dependence factor – see B.10.2
S
π temperature dependence factor – see B.10.3
T
Relay manufacturers are not required to demonstrate the achievement of the failure rate data
before delivery of a specific lot.
B.10 Stress factors
B.10.1 Electrical stress dependence factor π
ES
See Table B.1.
– 20 – 61811-10  IEC:2002
Table B.1 – Factor π
ES
Factor π for
ES
Stress region
a
See Figure 9 Resistive load Capacitive and Inductive load
of IEC 61709 incandescent lamp load
1 2 2
−
2 1 8 8
3 2 20 40
4 8 40 −
a
Maximum current peak stated in the relevant detail specification not to be exceeded.

B.10.2 Switching rate dependence factor π
S
This factor considers the number of operating cycles per hour (S).
a) π = 1 for 0,01 < S ≤ 1
S
b) π = S / S for S > 1
S ref
where
S is the number of operating cycles per hour;
S is the reference operating cycles per hour, where S = 1.
ref ref
The factor π is shown in Figure B.1.
S
π
S
0 1 2 3 4
2 1
− −
10 10 10 10 10
10 10
Operating cycles per hour  S
IEC  2972/02
Figure B.1 – Factor π depending on the operating cycles
S
61811-10  IEC:2002 – 21 –
B.10.3 Temperature dependence factor, π
T
See Table B.2.
Table B.2 – Factor π
T
Factor for the average ambient temperature
a
θ
amb
≤40 °C 70 °C 85 °C
1 1,8 2,3
a
Valid only up to the maximum permissible ambient temperature according to box (11) under 1.3 of the relevant
(blank) detail specification.
B.11 Example for calculation of the failure rate under actual operating
conditions
A relay certified according to a detail specification switches a resistive contact load of stress
region 1 (see Table B.1, and Figure 9 of IEC 61709) at an ambient temperature of 70 °C:
–7
λ = 10 ; U ≤ 0,5 V; I ≤ 0,1 A; ambient temperature θ = 70 °C
amb
What is the value of the failure rate under those conditions?
step (1): from equation under B.9: λ = λ × π × π × π
ref ES S T
step (2): from B.10.1, Table B.1, stress region 1: π = 2
ES
step (3): from B.10.2, Figure B.1, one cycle per hour: π = 1
S
step (4): from B.10.3, Table B.2, θ = 70 °C: π = 1,8
amb T
step (5): perform the calculation; thus the failure rate, under the conditions
stated above, is obtained as:
–7
λ = λ × π × π × π = 10 × 2 × 1 × 1,8 =
ref ES S T
–7
= 3,6 ⋅ 10 per operating cycle = 360 fit
step (6): perform the calculation according to E.2.4 of IEC 60255-23:
1 1
= 2,8 ⋅ 10 hours = 317 years
MTBF= =
−7
λ 3,6×10
The same procedure applies to the cycle-related mean time between failures (MTBF ). Details
c
and more information are given in E.2.1 to E.2.3 of normative Annex E of IEC 60255-23.
___________
– 22 – 61811-10  CEI:2002
SOMMAIRE
AVANT-PROPOS . 23

1 Généralités .
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