IEC 62912-2:2019

IEC 62912-2 ®
Edition 1.0 2019-08
INTERNATIONAL
STANDARD
Railway applications – Direct current signalling monostable relays –
Part 2: Spring type relays
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IEC 62912-2 ®
Edition 1.0 2019-08
INTERNATIONAL
STANDARD
Railway applications – Direct current signalling monostable relays –

Part 2: Spring type relays
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 45.060.01 ISBN 978-2-8322-7202-2

– 2 – IEC 62912-2:2019 © IEC 2019
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 7
2 Normative references . 7
3 Terms and definitions . 7
4 Essential requirements of the relays and their construction. 11
4.1 Generic requirements. 11
4.1.1 Generic requirements for spring type signalling relays . 11
4.1.2 Forcibly guided contacts . 11
4.1.3 Forcibly guided operation . 11
4.1.4 Degradation during service . 11
4.2 Specific requirements . 11
4.2.1 Non-welding characteristics . 11
4.2.2 Opening of make contacts . 11
4.2.3 Mounting orientation . 12
4.3 Mechanical construction . 12
4.3.1 Connecting device . 12
4.3.2 Materials and arrangement . 12
4.3.3 Prevention of spring breakage . 12
4.3.4 Prevention of screw loosening . 12
4.4 Environmental conditions . 13
4.4.1 General . 13
4.4.2 Vibrations and shocks . 13
4.5 Magnetic system . 13
4.5.1 Anti-residual magnetism design . 13
4.5.2 Function . 13
4.6 Design of insulation . 13
4.6.1 General . 13
4.6.2 Overvoltage . 14
4.6.3 Test voltage . 14
4.6.4 Pollution . 14
4.7 Contacts . 14
4.7.1 Spacing (contact gap) . 14
4.7.2 Break contact . 14
4.7.3 Contact heating . 15
4.7.4 Service life . 15
4.7.5 Minimum distance apart of the relay contact elements . 15
4.7.6 Contact force . 15
4.7.7 Opening force of contacts . 15
4.7.8 Self-cleaning . 16
4.7.9 Bounce . 16
4.7.10 Contact resistance . 16
5 Application conditions . 16
6 Measurement and test methods . 16

Annex A (normative) Modified Goodman diagram. 18
A.1 Modified Goodman diagram . 18
A.2 Calculation method for maximum stress of return spring . 18
A.3 Stress calculation example of return spring . 20
Annex B (informative) Example of service life agreement (lifetime expectation) . 22
Annex C (informative) Method of measuring the opening force of contacts . 23
Bibliography . 24

Figure A.1 – Modified Goodman diagram . 18
Figure A.2 – Example of railway direct current signalling monostable relay . 19
Figure A.3 – Stress calculation model of return spring . 19
Figure A.4 – Plot for an example stress of return spring at Modified Goodman Diagram . 21
Figure C.1 – Method of measuring the opening force of contacts . 23

Table 1 – Contact resistance . 16
Table 2 – List of measurement and test items . 17
Table B.1 – Example of service life agreement (minimum number of movements) . 22

– 4 – IEC 62912-2:2019 © IEC 2019
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
RAILWAY APPLICATIONS – DIRECT CURRENT
SIGNALLING MONOSTABLE RELAYS –

Part 2: Spring type relays
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
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International Standard IEC 62912-2 has been prepared by IEC technical committee 9:
Electrical equipment and systems for railways.
The text of this International Standard is based on the following documents:
FDIS Report on voting
9/2513/FDIS 9/2532/RVD
Full information on the voting for the approval of this International Standard can be found in
the report on voting indicated in the above table.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.

The existing IEC 62912 will be renumbered as IEC 62912-1 on the occasion of its next
revision.
A list of all parts in the IEC 62912 series, published under the general title Railway
applications – Direct current signalling monostabe relays, can be found on the IEC website.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to
the specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
A bilingual version of this publication may be issued at a later date.

– 6 – IEC 62912-2:2019 © IEC 2019
INTRODUCTION
This document gives a set of generic and specific requirements for non-proved direct current
signalling relays of the spring type.
This document introduces a set of recommendations and requirements for signalling relay
characteristics, construction, magnetic system, contacts and insulation. Requirements are
coordinated with current International Standards on all-or-nothing relays.
This document is in addition to IEC 62912:2015. IEC 62912-2 describes the non-proved
spring type relay.
All signalling relays are expected to fulfil the requirements of IEC 62425:2007 and their
characteristics are given by IEC 62425:2007, Annex C.7.22 which lists two types of physical
properties to provide return forces for stability. Of these properties IEC 62912-2 considers
only relays with a spring return force alone.
Meeting all the requirements in IEC 62912-2 is sufficient to ensure that further compliance to
IEC 62425:2007 need not be evaluated.
IEC 62912-2 has been developed as a standard independent from IEC 62912:2015. It uses
the same structure as IEC 62912:2015. IEC 62912-2 does not refer to the IEC 61810 series
because the relays defined in it are exclusively used in the signalling system, unlike the
electromagnetic type elementary relays defined by IEC 61810.

RAILWAY APPLICATIONS – DIRECT CURRENT
SIGNALLING MONOSTABLE RELAYS –

Part 2: Spring type relays
1 Scope
This document gives requirements for direct current relays intended for safety-related
applications in railway signalling installations.
This document is applicable to non-proved signalling monostable relays of the spring type,
whose return force is generated by elasticity of spring.
The return force can be provided either from a separate spring and/or from the contact
springs themselves.
NOTE “Non-proved” means the feature of relays fulfilling all the safety conditions without the aid of other relays or
without control of operations in the circuit.
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 62425:2007, Railway applications – Communication, signalling and processing systems –
Safety related electronic systems for signalling
IEC 62497-1, Railway applications – Insulation coordination – Part 1: Basic requirements –
Clearances and creepage distances for all electrical and electronic equipment
IEC 62498-3:2010, Railway applications – Environmental conditions for equipment – Part 3:
Equipment for signalling and telecommunications
IEC 62912:2015, Railways applications – Direct current signalling monostable relays of type N
and type C
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1
all-or-nothing relay
electrical relay, which is intended to be energised by a quantity, the value of which is either
within its operative range or effectively zero
Note 1 to entry: “All-or-nothing relays” include both “elementary relays” and “time relays”.
[SOURCE: IEC 60050-444:2002, 444-01-02]

– 8 – IEC 62912-2:2019 © IEC 2019
3.2
armature
moveable part of a relay that controls contact members
[SOURCE: IEC 62912:2015, 3.2]
3.3
bounce time
for a contact which is closing/opening its circuit, time interval between the instant when the
contact circuit first closes/opens and the instant when the circuit is finally closed/opened
[SOURCE: IEC 60050-444:2002, 444-05-04]
3.4
break contact
contact which is open when the relay is in its operate condition and which is closed when the
relay is in its release condition
[SOURCE: IEC 60050-444:2002, 444-04-18]
3.5
change-over contact
combination of two contact circuits with three contact members, one of which is common to
the two contact circuits; such that when one of these contact circuits is open, the other is
closed
[SOURCE: IEC 60050-444:2002, 444-04-19]
3.6
contact force
force which two contact members exert against each other at their contact points in the closed
position
[SOURCE: IEC 60050-444:2002, 444-04-10]
3.7
contact gap
gap between the contact points when the contact circuit is open
[SOURCE: IEC 60050-444:2002, 444-04-09]
3.8
contact member
conductive part designed to co-act with another to close or open the output circuit
[SOURCE: IEC 60050-444:2002, 444-04-05]
3.9
contact point
part of a contact member at which the contact circuit closes or opens
[SOURCE: IEC 60050-444:2002, 444-04-06]
3.10
contact resistance
resistance of a mated set of contacts under specified conditions
[SOURCE: IEC 60050-581:2008, 581-23-08]

3.11
contact wipe
relative rubbing movement of contact points after they have touched
[SOURCE: IEC 60050-444:2002, 444-04-12]
3.12
drop-away current
maximum current through the coil that, starting from the nominal current value, produces the
opening of all the make contacts
[SOURCE: IEC 62912:2015, 3.12]
3.13
elementary relay
all-or-nothing relay which operates and releases without any intentional time delay
[SOURCE: IEC 60050-444:2002, 444-01-03]
3.14
forcibly guided contacts
combination of make contacts and break contacts designed in such a way that it is made sure
by mechanical means that these make contacts and break contacts can never be in the closed
position simultaneously
[SOURCE: IEC 60050-444:2002, 444-04-23]
3.15
maintenance test
test carried out periodically on an item to verify that its performance remains within specified
limits, after having made certain adjustments, if necessary
[SOURCE: IEC 60050-151:2001, 151-16-25]
3.16
make contact
contact which is closed when the relay is in its operate condition and which is opened when
the relay is in its release condition
[SOURCE: IEC 60050-444:2002, 444-04-17]
3.17
monostable relay
electrical relay which, having responded to an energising quantit
...