IEC 60085:2007

IEC 60085
Edition 4.0 2007-11
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Electrical insulation – Thermal evaluation and designation

Isolation électrique – Evaluation et désignation thermiques

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IEC 60085
Edition 4.0 2007-11
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Electrical insulation – Thermal evaluation and designation

Isolation électrique – Evaluation et désignation thermiques

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
H
CODE PRIX
ICS 29.035.01; 17.220.99 ISBN 2-8318-9387-9

– 2 – 60085 © IEC:2007
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ELECTRICAL INSULATION –
THERMAL EVALUATION AND DESIGNATION

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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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 60085 has been prepared by technical committee 112: Evaluation
and qualification of electrical insulating materials and systems.
This fourth edition cancels and replaces the third edition, published in 2004, and constitutes a
technical revision.
The major technical changes with regard to the previous edition concern the fact that this
edition is an amalgamation of the third edition of this standard together with IEC 62114:2001.
The text of this standard is based on the following documents:
FDIS Report on voting
112/74/FDIS 112/77/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.

60085 © IEC:2007 – 3 –
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.
– 4 – 60085 © IEC:2007
ELECTRICAL INSULATION –
THERMAL EVALUATION AND DESIGNATION

1 Scope
This International Standard now distinguishes between thermal classes for electrical
insulation systems and electrical insulating materials. It establishes the criteria for evaluating
the thermal endurance of either electrical insulating materials (EIM) or electrical insulation
systems (EIS). It also establishes the procedure for assigning thermal classes.
This standard is applicable where the thermal factor is the dominant ageing factor.
NOTE A thermal class is not assigned to an EIM as related to its use in an EIS
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 60216-1: Electrical insulating materials – Properties of thermal endurance – Part 1:
Ageing procedures and evaluation of test results
IEC 60216-5, Electrical insulating materials – Thermal endurance properties – Part 5:
Determination of relative thermal endurance index (RTE) of an insulating material
IEC 60505: Evaluation and qualification of electrical insulation systems
IEC 61857 (all parts), Electrical insulation systems – Procedures for thermal evaluation
IEC 61858, Electrical insulation systems – Thermal evaluation of modifications to an
established wire-wound EIS
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60505, as well as
the following, apply.
3.1
electrical insulating material
(EIM)
solid or fluid with negligibly low electric conductivity, or a simple combination of such
materials, used to separate conducting parts at different electrical potential in electrotechnical
devices
NOTE 1 A “simple combination” may be a combination of EIM delivered in a joint state, for example, a flexible
material consisting of a paper laminated on polyethylene terephthalate film.
NOTE 2 For testing purposes, electrodes may be applied on material specimens without this combination formally
constituting an EIS to be tested as such.

60085 © IEC:2007 – 5 –
3.2
electrical insulation system
(EIS)
insulating structure containing one or more EIM together with associated conducting parts
employed in an electrotechnical device
3.3
candidate EIM
EIM under evaluation to determine its estimated thermal endurance
3.4
reference EIM
material with known thermal endurance, preferably derived from service experience, used for
comparative tests with the candidate EIM
3.5
candidate EIS
EIS under evaluation to determine its service capability (thermal)
3.6
reference EIS
established EIS evaluated on the basis of either a known service experience record or a
known comparative functional evaluation
3.7
EIM assessed thermal endurance index
(EIM ATE)
numerical value of the temperature in degrees Celsius, up to which the reference EIM
possesses known, satisfactory service experience in the specified application
3.8
EIM relative thermal endurance index
(EIM RTE)
numerical value of the temperature in degrees Celsius at which the estimated time to endpoint
of the candidate EIM is the same as the estimated time to endpoint of the reference EIM at a
temperature equal to its EIM ATE
3.9
EIS assessed thermal endurance index
(EIS ATE)
numerical value of the temperature in degrees Celsius for the reference EIS as derived from
known service experience or a known comparative functional evaluation
3.10
EIS relative thermal endurance index
(EIS RTE)
numerical value of the temperature in degrees Celsius for the candidate EIS which is relative
to the known EIS ATE of a reference EIS, when both EIS are subjected to the same ageing
and diagnostic procedures in a comparative test
3.11
thermal class
designation that is equal to the numerical value of the recommended maximum continuous
use temperature in degrees Celsius
NOTE 1 EIS subjected to operating temperatures exceeding its assigned thermal class can result in shorter
expected life.
– 6 – 60085 © IEC:2007
NOTE 2 EIM with different thermal endurance indices (ATE/RTE according to IEC 60216-5) may be combined to
form an EIS which has a thermal class that may be higher or lower than the recommended maximum continuous
use temperature of any of the individual components according to IEC 60505.
4 General considerations – Relation of EIM to EIS
The description of an electrotechnical device as being of a particular thermal class does not
mean, and must not be taken to imply, that each EIM used in its construction is of the same
thermal endurance.
The thermal class for an EIS may not be directly related to the thermal endurance of the
individual EIM included in it. In the EIS, the protective character of other EIM used in the
system may improve the performance of an individual EIM allowing its use in an EIS with a
thermal class greater than the thermal endurance of the individual EIM. On the other hand,
problems of i
...