ASTM D1932-04
(Test Method)Standard Test Method for Thermal Endurance of Flexible Electrical Insulating Varnishes
Standard Test Method for Thermal Endurance of Flexible Electrical Insulating Varnishes
SIGNIFICANCE AND USE
A major factor affecting the long term performance of insulating materials is thermal degradation. Other factors, such as moisture and vibration, may cause failures after the material has been weakened by thermal degradation.
An electrical insulating varnish is effective in protecting electrical equipment only as long as it retains its physical and electrical integrity.
The thermal degradation of the varnish results in weight loss, porosity, crazing, and generally a reduction in flexibility. Degradation of the varnish can be detected by a decrease in dielectric strength, which is therefore used as the failure criterion for this test method.
Electrical insulating varnishes undergo flexing in service due to vibration and thermal expansion. For this reason, this functional test includes flexing and elongation of the insulation. The electrodes used in this test method are designed to elongate the outer surface of the specimen 2 % with respect to the neutral axis of the base fiber while being tested for dielectric breakdown.
SCOPE
1.1 This test method covers the determination of the relative thermal endurance of flexible electrical insulating varnishes by determining the time necessary at elevated temperatures to decrease the dielectric breakdown of the varnish to an arbitrarily selected value when applied to a standard glass fiber fabric.
1.2 This test method does not apply to varnishes that lose a high percentage of their dielectric breakdown voltage when flexed before elevated temperature exposure as prescribed in the screening test (Section 9). Examples of such varnishes are those used for high speed armatures and laminated structures. Also, this test method is not applicable to varnishes which distort sufficiently during thermal elevated temperature exposure so that they cannot be tested using the curved electrode assembly.
1.3 Thermal endurance is expressed in terms of a temperature index.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. For specific hazard statements, see Section 7.
1.5 The values stated in SI units are the standard.
There is no equivalent IEC or ISO standard.
General Information
Relations
Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information.
An American National Standard
Designation:D1932–04
Standard Test Method for
Thermal Endurance of Flexible Electrical Insulating
1
Varnishes
This standard is issued under the fixed designation D1932; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the Department of Defense.
1. Scope at Commercial Power Frequencies
D374 Test Methods for Thickness of Solid Electrical Insu-
1.1 Thistestmethodcoversthedeterminationoftherelative
lation
thermal endurance of flexible electrical insulating varnishes by
D580 Specification for Greige Woven Glass Tapes and
determining the time necessary at elevated temperatures to
Webbings
decrease the dielectric breakdown of the varnish to an arbi-
D1346 Methods of Testing Electrical Insulating Varnishes
trarily selected value when applied to a standard glass fiber
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for 180°C and Above
fabric.
D1711 Terminology Relating to Electrical Insulation
1.2 This test method does not apply to varnishes that lose a
D2518 Specification for Woven Glass Fabrics for Electrical
high percentage of their dielectric breakdown voltage when
Insulation
flexed before elevated temperature exposure as prescribed in
D5423 Specification for Forced-Convection Laboratory
the screening test (Section 9). Examples of such varnishes are
Ovens for Evaluation of Electrical Insulation
those used for high speed armatures and laminated structures.
D6054 Practice for Conditioning Electrical Insulating Ma-
Also, this test method is not applicable to varnishes which
terials for Testing
distort sufficiently during thermal elevated temperature expo-
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2.2 IEEE Publications:
sure so that they cannot be tested using the curved electrode
IEEE No. 101A Guide for the Statistical Analysis of Ther-
assembly.
mal Life Test Data (including Appendix A)
1.3 Thermal endurance is expressed in terms of a tempera-
2.3 IEC Publications:
ture index.
IEC 60216 Guide for the Determination of Thermal Endur-
1.4 This standard does not purport to address all of the
5
ance Properties of Electrical Insulating Materials (Part 1)
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
3. Terminology
priate safety and health practices and determine the applica-
3.1 Definitions:
bility of regulatory limitations prior to use. For specific hazard
3.1.1 temperature index (TI), n—a number which permits
statements, see Section 7.
comparison of the temperature/time characteristics of an elec-
1.5 The values stated in SI units are the standard.
trical insulating material, or a simple combination of materials,
NOTE 1—There is no equivalent IEC or ISO standard.
based on the temperature in degrees Celsius which is obtained
by extrapolating the Arrhenius plot of endpoint time versus
2. Referenced Documents
temperature to a specified time, usually 20 000 h.
2
2.1 ASTM Standards:
3.1.2 thermal endurance graph, n—an Arrhenius plot.
D149 Test Method for Dielectric Breakdown Voltage and
3.1.3 thermal endpoint time, n—the time necessary for a
Dielectric Strength of Solid Electrical Insulating Materials
specific property of a material, or a simple combination of
materials, to degrade to a defined end point when aged at a
specified temperature.
1
This test method is under the jurisdiction of ASTM Committee D09 on
3.1.4 thermal life endpoint time, n—a graphical representa-
Electrical and Electronic Insulating Materials and is the direct responsibility of
tion of thermal endpoint time at a specified exposure tempera-
Subcommittee D09.01 on Electrical Insulating Varnishes, Powders, and Encapsu-
lating Compounds.
ture in which the value of a property of a material, or a simple
Current edition approved March 1, 2004. Published March 2004. Originally
approved in 1967. Last previous edition approved in 2003 as D1932 – 03. DOI:
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10.1520/D1932-04. Withdrawn.
2 4
For referenced ASTM standards, visit the ASTM website, www.astm.org, or Available from the Institute of Electrical and Electronics Engineers, 1828 LSt.,
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM NW, Suite 1202, Washington, DC 20036–5104.
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Standards volume information, refer to the standard’s Document Summary page on Available from American National Standards Institute, 25 West 43rd St., 4th
the ASTM website. Floor, New York, NY 10036.
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D1932–04
combination of materials, is measured at room temperat
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