IEC 61857-21:2009

IEC 61857-21 ®
Edition 3.0 2009-05
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Electrical insulation systems – Procedures for thermal evaluation –
Part 21: Specific requirements for general-purpose models – Wire-wound
applications
Systèmes d'isolation électrique – Procédures d'évaluation thermique –
Partie 21: Exigences particulières pour les modèles d'usage général –
Applications aux enroulements à fil

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IEC 61857-21 ®
Edition 3.0 2009-05
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Electrical insulation systems – Procedures for thermal evaluation –
Part 21: Specific requirements for general-purpose models – Wire-wound
applications
Systèmes d'isolation électrique – Procédures d'évaluation thermique –
Partie 21: Exigences particulières pour les modèles d'usage général –
Applications aux enroulements à fil

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
P
CODE PRIX
ICS 29.080.30 ISBN 978-2-88910-582-3
– 2 – 61857-21 © IEC:2009
CONTENTS
FOREWORD.3
INTRODUCTION.5
1 Scope.6
2 Normative references.6
3 Terms and definitions .6
4 Construction .7
4.1 General information .7
4.2 Model components .8
4.3 Assembly of the model.11
5 Number of test objects.12
6 Test procedure .12
6.1 General .12
6.2 Initial screening test.12
6.2.1 General .12
6.2.2 Initial dielectric test .12
6.3 Thermal endurance test .13
6.3.1 Endurance test cycle.13
6.3.2 Thermal ageing.13
6.3.3 Mechanical stress .13
6.3.4 Thermal shock .13
6.3.5 Moisture exposure .14
6.3.6 Dielectric diagnostic test .14
7 End-of-life criterion .14
8 Analysing, reporting and classification.15
Bibliography .16

Figure 1 – Photos of GPM and GPM-TC test objects.
Figure 2 – Schematic drawing of a GPM frame .9
Figure 3 – Manufacturing drawing of a GPM-TC frame.10

Table 1 – Initial dielectric test.13
Table 2 – Dielectric diagnostic test .14

61857-21 © IEC:2009 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
___________
ELECTRICAL INSULATION SYSTEMS –
PROCEDURES FOR THERMAL EVALUATION –

Part 21: Specific requirements for general-purpose models –
Wire-wound applications
FOREWORD
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International Standard IEC 61857-21 has been prepared by IEC technical committee 112:
Evaluation and qualification of electrical insulating materials and systems.
This third edition cancels and replaces the second edition published in 2004, and constitutes
editorial revisions to make this standard compatible with Parts 1 and 22.
The text of this standard is based on the following documents:
FDIS Report on voting
112/120/FDIS 112/126/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.

– 4 – 61857-21 © IEC:2009
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all the parts in the IEC 61857 series, under the general title Electrical insulation
systems – Procedures for thermal evaluation, can be found on the IEC website.
The committee has decided that the contents of this publication will remain unchanged until the
maintenance result date indicated on the IEC web site under "http://webstore.iec.ch" in the data
related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
61857-21 © IEC:2009 – 5 –
INTRODUCTION
A series of parts that will make up IEC 61857 is currently being developed, each of which will
address a specific test object and/or application with an associated test procedure.

– 6 – 61857-21 © IEC:2009
ELECTRICAL INSULATION SYSTEMS –
PROCEDURES FOR THERMAL EVALUATION –

Part 21: Specific requirements for general-purpose models –
Wire-wound applications
1 Scope
This part of IEC 61857 describes a general-purpose model (GPM) and a tall channel alternative
model (GPM-TC) which can be used for the evaluation of wire-wound electrical insulation
systems (EIS) where specific electr
...