Test procedure for the determination of the temperature index of enamelled and tape wrapped winding wires (IEC 60172:2020)

IEC 60172:2020  which contains the International Standard and its Redline version, showing all changes of the technical content compared to the previous edition.IEC 60172:2020 specifies, in accordance with the provisions of IEC 60216-1, a method for evaluating the temperature index of enamelled wire, varnished or unvarnished with an impregnating agent, and of tape wrapped round and rectangular wire, in air at atmospheric pressure by periodically monitoring changes in response to AC proof voltage tests. This procedure does not apply to fibre-insulated wire or wire covered with tapes containing inorganic fibres. NOTE The data obtained according to this test procedure provide the designer and development engineer with information for the selection of winding wire for further evaluation of insulation systems and equipment tests. This fifth edition cancels and replaces the fourth edition published in 2015. This edition constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition:
- revision of 3.1, definition of thermal index;
- revision of 3.3, time to failure;
- revisions to 5.1.1 for clarity and to reduce the range wire size range to which the test applies;
- revisions to 5.1.2 for tape wrapped round and enamelled or tape wrapped rectangular wire for clarity;
- revision to Clause 9 to add the correlation coefficient, r to the report.

Prüfverfahren zur Bestimmung des Temperaturindex von Lackdrähten und bandumwickelten Drähten (IEC 60172:2020)

Méthode d'essai pour la détermination de l'indice de température des fils de bobinage émaillés et enveloppés de ruban (IEC 60172:2020)

IEC 60172:2020 est disponible sous forme de IEC 60172:2020 RLV qui contient la Norme internationale et sa version Redline, illustrant les modifications du contenu technique depuis l'édition précédente.L'IEC 60172:2020 spécifie, conformément aux dispositions de l’IEC 60216-1, une méthode pour l’évaluation de l'indice de température du fil émaillé, imprégné ou non imprégné avec un matériau d’imprégnation, et du fil de section circulaire ou rectangulaire, enveloppé de ruban, dans l’air à la pression atmosphérique, en contrôlant périodiquement les variations de réponse aux essais de tension d'épreuve en courant alternatif. Cette méthode ne concerne pas le fil avec revêtement fibreux ou le fil recouvert de rubans contenant des fibres non organiques. NOTE Les données obtenues au moyen de cette méthode d'essai fournissent à l'ingénieur d'étude et de développement les informations pour sélectionner le fil de bobinage et obtenir une meilleure évaluation des systèmes isolants et des essais d'équipement. Cette cinquième édition annule et remplace la quatrième édition parue en 2015. Cette édition constitue une révision technique. Cette édition inclut les modifications techniques majeures suivantes par rapport à l'édition précédente: - révision du 3.1, définition d’indice thermique; - révision du 3.3, durée de fonctionnement avant défaillance; - révisions du 5.1.1 à des fins de clarification et pour limiter la plage des dimensions de fils à laquelle l’essai s’applique; - révisions à des fins de clarification du 5.1.2 relatif au fil de section circulaire enveloppé d'un ruban et au fil de section rectangulaire émaillé ou enveloppé d'un ruban; - révision de l’Article 9 afin d’ajouter le coefficient de corrélation, r au rapport.

Preskusni postopek za ugotavljanje temperaturnega indeksa emajlirane in s trakom ovite žice za navitja (IEC 60172:2020)

General Information

Status
Published
Publication Date
27-Jan-2021
Technical Committee
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
22-Jan-2021
Due Date
29-Mar-2021
Completion Date
28-Jan-2021

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SLOVENSKI STANDARD
SIST EN IEC 60172:2021
01-marec-2021
Nadomešča:
SIST EN 60172:2015
Preskusni postopek za ugotavljanje temperaturnega indeksa emajlirane in s
trakom ovite žice za navitja (IEC 60172:2020)

Test procedure for the determination of the temperature index of enamelled and tape

wrapped winding wires (IEC 60172:2020)
Prüfverfahren zur Bestimmung des Temperaturindex von Lackdrähten und
bandumwickelten Drähten (IEC 60172:2020)

Méthode d'essai pour la détermination de l'indice de température des fils de bobinage

émaillés et enveloppés de ruban (IEC 60172:2020)
Ta slovenski standard je istoveten z: EN IEC 60172:2021
ICS:
17.200.01 Termodinamika na splošno Thermodynamics in general
29.060.10 Žice Wires
SIST EN IEC 60172:2021 en

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN IEC 60172:2021
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SIST EN IEC 60172:2021
EUROPEAN STANDARD EN IEC 60172
NORME EUROPÉENNE
EUROPÄISCHE NORM
January 2021
ICS 29.060.10 Supersedes EN 60172:2015 and all of its amendments
and corrigenda (if any)
English Version
Test procedure for the determination of the temperature index of
enamelled and tape wrapped winding wires
(IEC 60172:2020)

Méthode d'essai pour la détermination de l'indice de Prüfverfahren zur Bestimmung des Temperaturindex von

température des fils de bobinage émaillés et enveloppés de Lackdrähten und bandumwickelten Drähten

ruban (IEC 60172:2020)
(IEC 60172:2020)

This European Standard was approved by CENELEC on 2020-12-28. 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 60172:2021 E
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SIST EN IEC 60172:2021
EN IEC 60172:2021 (E)
European foreword

The text of document 55/1876/FDIS, future edition 5 of IEC 60172, prepared by IEC/TC 55 "Winding

wires" was submitted to the IEC-CENELEC parallel vote and approved by CENELEC as
EN IEC 60172:2021.
The following dates are fixed:

• latest date by which the document has to be implemented at national (dop) 2021-09-28

level by publication of an identical national standard or by endorsement

• latest date by which the national standards conflicting with the (dow) 2023-12-28

document have to be withdrawn

This document supersedes EN 60172:2015 and all of its amendments and corrigenda (if any).

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.

Endorsement notice

The text of the International Standard IEC 60172:2020 was approved by CENELEC as a European

Standard without any modification.

In the official version, for Bibliography, the following notes have to be added for the standards

indicated:
IEC 60317 (series) NOTE Harmonized as EN 60317 (series)
IEC 60455-3-5 NOTE Harmonized as EN 60455-3-5
IEC 60464-3-2 NOTE Harmonized as EN 60464-3-2
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SIST EN IEC 60172:2021
EN IEC 60172:2021 (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 60216-1 - Electrical insulating materials - Thermal EN 60216-1 -
endurance properties - Part 1: Ageing
procedures and evaluation of test results
IEC 60216-3 - Electrical insulating materials - Thermal - -
endurance properties - Part 3: Instructions
for calculating thermal endurance
characteristics
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SIST EN IEC 60172:2021
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SIST EN IEC 60172:2021
IEC 60172
Edition 5.0 2020-11
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Test procedure for the determination of the temperature index of enamelled and
tape wrapped winding wires
Méthode d’essai pour la détermination de l’indice de température des fils de
bobinage émaillés et enveloppés de ruban
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 29.060.10 ISBN 978-2-8322-9086-6

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 60172:2021
– 2 – IEC 60172:2020 © IEC 2020
CONTENTS

FOREWORD ........................................................................................................................... 4

1 Scope .............................................................................................................................. 6

2 Normative references ...................................................................................................... 6

3 Terms and definitions ...................................................................................................... 6

4 Summary of procedure .................................................................................................... 7

5 Test specimens ............................................................................................................... 7

5.1 Preparation ............................................................................................................. 7

5.1.1 Enamelled non-tape wrapped round wire ......................................................... 7

5.1.2 Tape wrapped round wire and enamelled or tape wrapped rectangular

wire ............................................................................................................... 10

5.2 Varnish impregnation ............................................................................................ 12

5.3 Notes on number of test specimens ...................................................................... 13

5.4 Specimen holder .................................................................................................. 13

5.4.1 For specimens according to 5.1.1 .................................................................. 13

5.4.2 For specimens according to 5.1.2 .................................................................. 13

6 Temperature exposure................................................................................................... 14

7 Test voltage and its application .................................................................................... 15

8 Calculations .................................................................................................................. 16

8.1 Specimen failure time ........................................................................................... 16

8.2 Time to failure ....................................................................................................... 16

8.3 Linearity of data .................................................................................................... 16

8.4 Calculating and plotting thermal endurance and temperature index ....................... 17

9 Report ........................................................................................................................... 18

Annex A (normative) Method for calculation of the regression line ....................................... 19

Annex B (normative) Correlation coefficient ......................................................................... 24

Bibliography .......................................................................................................................... 25

Figure 1 – Device used to form enamelled round wire test specimen ...................................... 8

Figure 2 – Spacer ................................................................................................................... 8

Figure 3 – Twist forming jig ..................................................................................................... 9

Figure 4 – Test specimen set up in forming jig ........................................................................ 9

Figure 5 – Test specimen formed with loop cut ..................................................................... 10

Figure 6 – Jig for bending large magnet wire, dielectric test specimen .................................. 11

Figure 7 – Forming jig and test specimen .............................................................................. 12

Figure 8 – Specimen holder .................................................................................................. 13

Figure 9 – Thermal endurance graph – Temperature index ................................................... 17

Figure A.1 – Plot of regression line based on sample calculation (Table A.2) ........................ 23

Table 1 – Force and number of twists for specimens ............................................................... 8

Table 2 – Proof voltage for round enamelled wire ................................................................. 10

Table 3 – Recommended exposure times in days per cycle................................................... 14

Table 4 – Proof voltage for tape-wrapped round and for enamelled or tape-wrapped

rectangular wire .................................................................................................................... 15

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SIST EN IEC 60172:2021
IEC 60172:2020 © IEC 2020 – 3 –
Table A.1 – Commonly used test temperatures in degrees Celsius and the

corresponding kelvins with its reciprocal and reciprocal squared values ................................ 21

Table A.2 – Sample calculation ............................................................................................. 22

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SIST EN IEC 60172:2021
– 4 – IEC 60172:2020 © IEC 2020
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
TEST PROCEDURE FOR THE DETERMINATION OF THE TEMPERATURE
INDEX OF ENAMELLED AND TAPE WRAPPED WINDING WIRES
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.

International Standard IEC 60172 has been prepared by IEC Technical Committee 55:

Winding wires.

This fifth edition cancels and replaces the fourth edition published in 2015. This edition

constitutes a technical revision.

This edition includes the following significant technical changes with respect to the previous

edition:
– revision of 3.1, definition of thermal index;
– revision of 3.3, time to failure;

– revisions to 5.1.1 for clarity and to reduce the range wire size range to which the test

applies;

– revisions to 5.1.2 for tape wrapped round and enamelled or tape wrapped rectangular wire

for clarity;
– revision to Clause 9 to add the correlation coefficient, r to the report.
---------------------- Page: 10 ----------------------
SIST EN IEC 60172:2021
IEC 60172:2020 © IEC 2020 – 5 –
The text of this International Standard is based on the following documents:
FDIS Report on voting
55/1876/FDIS 55/1893/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 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.

IMPORTANT – The 'colour inside' logo on the cover page of this publication 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.
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SIST EN IEC 60172:2021
– 6 – IEC 60172:2020 © IEC 2020
TEST PROCEDURE FOR THE DETERMINATION OF THE TEMPERATURE
INDEX OF ENAMELLED AND TAPE WRAPPED WINDING WIRES
1 Scope

This International Standard specifies, in accordance with the provisions of IEC 60216-1, a

method for evaluating the temperature index of enamelled wire, varnished or unvarnished with

an impregnating agent, and of tape wrapped round and rectangular wire, in air at atmospheric

pressure by periodically monitoring changes in response to AC proof voltage tests. This

procedure does not apply to fibre-insulated wire or wire covered with tapes containing

inorganic fibres.

NOTE The data obtained according to this test procedure provide the designer and development engineer with

information for the selection of winding wire for further evaluation of insulation systems and equipment tests.

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 60216-1, Electrical insulating materials – Thermal endurance properties – Part 1: Ageing

procedures and evaluation of test results

IEC 60216-3, Electrical insulating materials – Thermal endurance properties – Part 3:

Instructions for calculating thermal endurance characteristics
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
temperature index

number which permits comparison of the temperature/time characteristics of an electrical

insulating material, or a simple combination of materials, based on the temperature in degrees

Celsius which is obtained by extrapolating the Arrhenius plot of life versus temperature to a

lifetime of 20 000 h

Note 1 to entry: In case of insulation systems, the temperature index may be derived from known service

experience or from a known comparative functional evaluation of an evaluated and established reference insulation

system as basis.

[SOURCE: IEC 60050-212:2010, 212-12-11] modified by merging Note 1 into the definition,

and to specify a lifetime of 20 000 h.]
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SIST EN IEC 60172:2021
IEC 60172:2020 © IEC 2020 – 7 –
3.2
specimen failure time

number of hours at the exposure temperature that have elapsed at the time a specimen

fails the proof test
3.3
time to failure

number of hours to failure calculated from the specimen mean value or logarithmic mean

value failure times for a set of specimens at one exposure temperature, in accordance with

8.2
4 Summary of procedure

A set of specimens in accordance with Clause 5 is subjected to a testing cycle. This cycle

consists of a heat-exposure period at a temperature given in Clause 6, followed by a proof

voltage test at room temperature in accordance with Clause 7.

This cycle is repeated until a sufficient number of specimens has failed. The time to failure is

calculated in accordance with Clause 8. The test is carried out at three or more

temperatures. A regression line is calculated in accordance with 8.4 and the time to failure

values plotted on thermal endurance graph paper as a function of the exposure
temperature.

The temperature in degrees Celsius, corresponding to the point of intersection of the

regression line with the ordinate of 20 000 h endurance represents the temperature index of

the winding wire under test.
5 Test specimens
5.1 Preparation
5.1.1 Enamelled non-tape wrapped round wire

This procedure applies to enamelled round wires that are not tape wrapped. The thermal

index can be determined by evaluating enamelled non-tape wrapped round wire with a

nominal conductor diameter of 0,224 mm up to and including 2,65 mm.

NOTE For round enamelled winding wires, experience has shown that nominal conductor diameters of 0,800 mm

up to and including 1,60 mm are generally found convenient to handle and test.

Wires with a nominal conductor diameter between 0,280 mm and 0,500 mm are permitted for

use when the specification range of diameters is limited to 0,500 mm and finer.

The grade of insulation used for determining the thermal index shall be grade 2 or grade 2B

for self-bonding winding wires.
Specimens shall be prepared as follows:

a) A wire specimen approximately 400 mm in length shall be twisted together over a distance

of 125 mm with a device as shown in Figure 1. The force (weight) applied to the wire pair

while being twisted and the number of twists are specified in Table 1.
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SIST EN IEC 60172:2021
– 8 – IEC 60172:2020 © IEC 2020
Figure 1 – Device used to form enamelled round wire test specimen
Table 1 – Force and number of twists for specimens
Nominal diameter Force applied to Number of twists
wire pairs per
mm N 125 mm
Over Up to and
including
0,224 0,25 0,85 33
0,25 0,35 1,7 23
0,35 0,50 3,4 16
0,50 0,75 7,0 12
0,75 1,05 13,5 8
1,05 1,50 27,0 6
1,50 2,15 54,0 4
2,15 2,65 108,0 3

b) Spacers may be prepared as shown in Figure 2. Such thermally stable insulating

materials as ceramic or silicone glass fibre laminate may be used. The spacers are

marked with a suitable identifying letter or number.
Dimensions in millimetres
Material: Silicone glass laminate
Figure 2 – Spacer
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SIST EN IEC 60172:2021
IEC 60172:2020 © IEC 2020 – 9 –

c) The test specimens may be shaped in a jig, an engineering drawing of which is shown

in Figure 3. A specimen is placed in the jig and a spacer, placed on the parallel leads

of the twisted pair, is brought up to the face of the jig as shown in Figure 4. The leads

are then bent parallel to hold the spacer in position. The forming jig provides more

uniform test specimens. If a specimen holder is used, the spacers are unnecessary.

Dimensions in millimetres
R = Radius of bend
Figure 3 – Twist forming jig
Figure 4 – Test specimen set up in forming jig

d) The loop at the end of the twisted section shall be cut at two places (not one) to

provide the maximum spacing between the cut ends as shown in Figure 5. Any bending

of the wires, at this end or the other untwisted end, to ensure adequate separation

between the wires shall avoid sharp bends or damage to the insulation.
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SIST EN IEC 60172:2021
– 10 – IEC 60172:2020 © IEC 2020
Figure 5 – Test specimen formed with loop cut

In order to ensure homogeneity of the set of test specimens, it is recommended that test

specimens be subjected to, and withstand without breakdown, a test voltage three times the

value given in Table 2 for 1 s prior to starting thermal exposure cycling.
Table 2 – Proof voltage for round enamelled wire
Increase in diameter due to the insulation Voltage
(mm) (rms)
Over Up to and including
– 0,015 300
0,015 0,024 300
0,024 0,035 400
0,035 0,050 500
0,050 0,070 700
0,070 0,090 1 000
0,090 0,130 1 200
5.1.2 Tape wrapped round wire and enamelled or tape wrapped rectangular wire

This procedure applies to any convenient dimension of tape wrapped round or tape wrapped

or enamelled rectangular wire.

It is recommended to select a wire having dimensions that minimize the bending force

necessary to shape the test specimen, since wire with high stiffness will yield specimens with

poor wire-to-wire contact areas.
Specimens shall be prepared as follows:

a) Two straight specimens of wire each of 250 mm length shall be cut from the supply spool.

b) 10 mm to 15 mm of the insulation shall be removed from one end of each piece of wire to

provide for electrical connection.

c) Each specimen shall be formed in a jig, as shown in Figure 6. This produces a straight

centre section of about 150 mm with bent ends, which provide the necessary flare at both

ends of the final specimen.
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SIST EN IEC 60172:2021
IEC 60172:2020 © IEC 2020 – 11 –
Dimensions in millimetres
Figure 6 – Jig for bending large magnet wire, dielectric test specimen
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SIST EN IEC 60172:2021
– 12 – IEC 60172:2020 © IEC 2020

d) The two formed specimens shall be placed together back-to-back and tightly wrapped with

glass yarn over the straight centre section of the specimen, as shown in Figure 7.

Figure 7 – Forming jig and test specimen

Care shall be taken that the centre section shows a close contact between the two pieces.

After tying, further bending of the ends shall be avoided. Pre-annealing of the specimen

prior to testing or impregnating will remove stress and craze marks and therefore may be

desirable with certain material.

e) Prior to starting the thermal exposure cycles, the specimen shall be proof-tested at

1 000 V AC.
5.2 Varnish impregnation

Insulated wire according to IEC 60317 and impregnating agents according to IEC 60455-3-5

or IEC 60464-3-2 can affect one another during the thermal ageing process.

NOTE 1 Testing varnished specimens will allow for evaluation of the compatibility of the wire insulation with an

impregnating agent. Thus, the temperature indices of different combinations can be compared.

Interaction between wire insulation and such agent may increase or decrease the relative

thermal life of this combination compared with the life of the wire tested without impregnation.

Therefore, with impregnated specimens, this test procedure may give an indication of the

thermal endurance of a combination of wire insulation and impregnating agent.
If such impregnation is required, the following procedure shall be applied:
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SIST EN IEC 60172:2021
IEC 60172:2020 © IEC 2020 – 13 –

With the specimen in the vertical position, it shall be immersed in the impregnating agent for

(60 ± 10) s. It shall be removed slowly and uniformly at a rate of about 1 mm/s. It shall be

drained horizontally for 10 min to 15 min and cured horizontally according to the

manufacturer's recommendation or to an agreed schedule. If more than one treatment is to be

given, immerse, drain and cure the specimen vertically reversing the specimen for each

subsequent treatment.

NOTE 2 Some impregnating agents, such as high viscosity or thixotropic products require alternative processing

methods.
5.3 Notes on number of test specimens

The accuracy of the test results depends largely upon the number of test specimens aged at

each temperature. A greater number of test specimens is required to achieve an acceptable

degree of accuracy if there is a wide spread in results among the specimens exposed at each

temperature.

Experience has shown that twenty specimens without impregnation and ten specimens with

impregnation give results with an acceptable tolerance. A minimum of ten specimens shall be

used.
5.4 Specimen holder
5.4.1 For specimens according to 5.1.1

Since individual handling of the twisted specimens may result in premature failures, it is

recommended that the specimens be placed in a suitable holder, as shown in Figure 8. The

holder should be designed in a manner that will protect the twisted specimens from external

mechanical damage and warping. The holder will be so constructed as to allow the ends of

the twist to protrude from the holder to make electrical connections for proof testing. The

holder shall be designed for at least ten specimens to decrease handling time.
Figure 8 – Specimen holder
5.4.2 For specimens according to 5.1.2
The specimen shall be hung in the oven. No special holder is required.
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SIST EN IEC 60172:2021
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6 Temperature exposure
Test specimens shall be subjected to the temperatures given in this Clause 6.

The test temperature and time of exposure in each cycle are given in Table 3. A test cycle is

defined as one exp
...

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