IEC 60371-3-5:2005

INTERNATIONAL IEC
STANDARD 60371-3-5
Second edition
2005-11
Insulating materials based on mica –
Part 3:
Specifications for individual materials –
Sheet 5: Glass-backed mica paper with an
epoxy resin binder for post-impregnation (VPI)
Reference number
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INTERNATIONAL IEC
STANDARD 60371-3-5
Second edition
2005-11
Insulating materials based on mica –
Part 3:
Specifications for individual materials –
Sheet 5: Glass-backed mica paper with an
epoxy resin binder for post-impregnation (VPI)

 IEC 2005  Copyright - all rights reserved
No part of this publication may be reproduced or utilized in any form or by any means, electronic or
mechanical, including photocopying and microfilm, without permission in writing from the publisher.
International Electrotechnical Commission, 3, rue de Varembé, PO Box 131, CH-1211 Geneva 20, Switzerland
Telephone: +41 22 919 02 11 Telefax: +41 22 919 03 00 E-mail: inmail@iec.ch Web: www.iec.ch
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Commission Electrotechnique Internationale L
International Electrotechnical Commission
МеждународнаяЭлектротехническаяКомиссия
For price, see current catalogue

– 2 – 60371-3-5  IEC:2005(E)
CONTENTS
FOREWORD.3
INTRODUCTION.5

1 Scope.6
2 Normative references .6
3 Designation .6
4 Requirements: raw materials .8
4.1 Mica paper .8
4.2 Glass fabric .8
4.3 Epoxy resin .8
5 Requirements: composition and tolerances.8
6 Requirements for material (as received) .9
6.1 General .9
6.2 Width .9
6.3 Thickness.9
6.4 Length.9
6.5 Cores .9
6.6 Joins .10
6.7 Tensile strength in the warp direction .10
6.8 Stiffness .10
6.9 Air permeance.10
7 Packing .10

Table 1 – Composition low bond, with a resin content in the range (8 ± 3) % .7
Table 2 – Composition medium bond, with a resin content in the range (16 ± 3) % .8
Table 3 – Tolerance on width.9
Table 4 – Air porosity.10

60371-3-5  IEC:2005(E) – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
INSULATING MATERIALS BASED ON MICA –

Part 3: Specifications for individual materials –
Sheet 5: Glass-backed mica paper with an epoxy resin binder
for post-impregnation (VPI)
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
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patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 60371-3-5 has been prepared by IEC technical committee 15:
Standards on specifications for electrical insulating materials.
This second edition cancels and replaces the first edition, published in 1992, and constitutes
a technical revision.
The main changes with regard to the previous edition include adjustments needed to align this
standard with changes included in the latest edition of IEC 60371-2.

– 4 – 60371-3-5  IEC:2005(E)
The text of this standard is based on the following documents:
FDIS Report on voting
15/228/FDIS 15/246/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.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
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.
A bilingual version of this publication may be issued at a later date.

60371-3-5  IEC:2005(E) – 5 –
INTRODUCTION
This part of IEC 60371 forms part of a series which deals with insulating materials built up
from mica splittings or mica paper with or without reinforcement, and with mica paper in its
pure state for use in electrical equipment.
IEC 60371 consists of three parts under the main title Specification for insulating materials
based on mica:
Part 1: Definitions and general requirements
Part 2: Methods of test
Part 3: Specifications for individual materials
This standard contains one of the sheets comprising part 3, as follows:
Sheet 5: Glass-backed mica paper with an epoxy resin binder for post-impregnation
(VPI – vacuum pressure impregnation)

– 6 – 60371-3-5  IEC:2005(E)
INSULATING MATERIALS BASED ON MICA –

Part 3: Specifications for individual materials –
Sheet 5: Glass-backed mica paper with an epoxy resin binder
for post-impregnation (VPI)
1 Scope
This part of IEC 60371 gives requirements for electrical insulating materials made by
combining mica paper with glass fabric and bonding them together with a small amount of
epoxy resin. The material is supplied in a flexible state and is designed for use in conjunction
with vacuum pressure impregnation (VPI) with compatible impregnates. The final cured
properties will be primarily dependent on the VPI resin used.
Two bond contents are specified:
– low bond with a resin content of (8 ± 3) %;
– medium bond with a resin content of (16 ± 3) %.
Materials which conform to this specification meet established levels of performance.
However, the selection of a material by a user for a specific application should be based on
the actual requirements necessary for adequate performance in that application and not
based on this specification alone.
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 60371-2:2004, Specification for insulating materials based on mica – Part 2: Methods
of test
IEC 60371-3-2, Insulating materials based on mica – Part 3: Specifications for individual
materials – Sheet 2: Mica paper
ISO 5636-5:2003, Paper and board – Determination of air permeance and air resistance
(medium range) – Part 5: Gurley method
3 Designation
When ordering materials to this specification only the specification and type numbers need be
quoted (see Tables 1 and 2).
Example: IEC 60371-3-5: type 5.1.01
The type number is derived from:
– the specification sheet number 5
– plus the sheet table number 5.1
– plus the number of the product in the sheet table 5.1.01

60371-3-5  IEC:2005(E) – 7 –
The descriptive code quoted in Tables 1 and 2, for example G23/M80/R08 for type 5.1.01,
Table 1, is derived from:
– glass content (G) 23 g/m²
– muscovite mica content (M) 80 g/m²
– resin content (R) 8 ± 3 %.
NOTE For phlogopite mica paper the letter "M" is replaced by the letter "P".
Table 1 – Composition low bond, with a resin content in the range (8 ± 3) %
Glass Mica Mass/ Permissable thickness
content content unit area range
Volatile
2 2 2
mm
g/m g/m g/m content
Type Descriptive code
max. %
Nom. Tol. Nom. Tol. Nom. Tol. Mean Individual
± ± ±
5.1.01 G23/M80/R08 23 2 80 7 112 12 0,08-0,12 0,07-0,13 0,5
5.1.02 G23/P80/R08 23 2 80 7 112 12 0,08-0,12 0,07-0,13 0,5
5.1.03 G23/M120/R08 23 2 120 10 155 15 0,09-0,13 0,08-0,14 0,5
5.1.04 G23/P120/R08 23 2 120 10 155 15 0,09-0,13 0,08-0,14 0,5
5.1.05 G32/M120/R08 32 3 120 1
...