ASTM D7894/D7894M-19
(Test Method)Standard Test Method for Thermal Endurance of Coating Powders Used for Integral Bus Bar Insulation Systems
Standard Test Method for Thermal Endurance of Coating Powders Used for Integral Bus Bar Insulation Systems
SIGNIFICANCE AND USE
5.1 A major factor affecting the life of insulating materials is thermal degradation. It is possible that other factors, such as moisture and vibration, will cause failures after the material has been weakened by thermal degradation.
5.2 Electrical insulation is effective in electrical equipment only as long as it retains its physical and electrical integrity. The following are potential indicators of thermal degradation: weight change, porosity, crazing, and generally a reduction in flexibility. Thermal degradation is usually accompanied by an ultimate reduction in dielectric breakdown.
5.3 This test method is useful in determining the thermal endurance of coating powders applied over a copper or aluminum substrate material.
SCOPE
1.1 This test method provides a procedure for evaluating thermal endurance of coating powders by determining the length of aging time at selected elevated temperatures required to achieve dielectric breakdown at room temperature at a pre-determined proof voltage. Thermal endurance is expressed in terms of a temperature index.
1.2 This test method is applicable to insulating powders used over a substrate material of copper or aluminum.
1.3 Units—The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system are not necessarily exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems is likely to result in non-conformance with the standard.
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, health, and environmental practices and determine the applicability of regulatory limitations prior to use. Specific precautionary statements are given in Section 7.
1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
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Standards Content (Sample)
This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D7894/D7894M − 19
Standard Test Method for
Thermal Endurance of Coating Powders Used for Integral
1
Bus Bar Insulation Systems
This standard is issued under the fixed designation D7894/D7894M; 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.
1. Scope at Commercial Power Frequencies
D1711 Terminology Relating to Electrical Insulation
1.1 This test method provides a procedure for evaluating
D5423 Specification for Forced-Convection Laboratory Ov-
thermal endurance of coating powders by determining the
ens for Evaluation of Electrical Insulation
length of aging time at selected elevated temperatures required
3
2.2 IEEE Document:
to achieve dielectric breakdown at room temperature at a
IEEE 101A Simplified Method for Calculation of the Re-
pre-determined proof voltage. Thermal endurance is expressed
gression Line
in terms of a temperature index.
1.2 This test method is applicable to insulating powders
3. Terminology
used over a substrate material of copper or aluminum.
3.1 Definitions:
1.3 Units—The values stated in either SI units or inch-
3.1.1 For definitions of terms used in this test method refer
pound units are to be regarded separately as standard. The
to Terminology D1711.
values stated in each system are not necessarily exact equiva-
3.2 Definitions of Terms Specific to This Standard:
lents; therefore, each system shall be used independently of the
3.2.1 thermal endurance, n—an expression for the stability
other. Combining values from the two systems is likely to
of an electrical insulating material, or a simple combination of
result in non-conformance with the standard.
materials, when maintained at elevated temperatures for ex-
tended periods of time.
1.4 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
4. Summary of Test Method
responsibility of the user of this standard to establish appro-
priate safety, health, and environmental practices and deter- 4.1 Specimens are aged in air at a minimum of three
mine the applicability of regulatory limitations prior to use.
temperatures above the expected use temperature of the mate-
Specific precautionary statements are given in Section 7.
rial. Exposure to ambient stress conditions, followed by
1.5 This international standard was developed in accor-
dielectric proof voltage tests in an electrically conductive
dance with internationally recognized principles on standard-
solution, are periodically conducted to determine the time of
ization established in the Decision on Principles for the
aging at each elevated temperature required to reduce the
Development of International Standards, Guides and Recom-
breakdown voltage to a pre-selected percentage of the original
mendations issued by the World Trade Organization Technical
breakdown value. These thermal life values are used to
Barriers to Trade (TBT) Committee.
construct a thermal endurance graph by means of which it is
possible to estimate a temperature index, corresponding to a
2. Referenced Documents
thermal life as specified in the material specification or as
2
2.1 ASTM Standards: agreed upon between the user and the supplier. It is possible
D149 Test Method for Dielectric Breakdown Voltage and that a material will have multiple indices, each corresponding
to a different thermal life as required by a given application.
Dielectric Strength of Solid Electrical Insulating Materials
5. Significance and Use
1
This test method is under the jurisdiction of ASTM Committee D09 on
5.1 Amajorfactoraffectingthelifeofinsulatingmaterialsis
Electrical and Electronic Insulating Materials and is the direct responsibility of
Subcommittee D09.01 on Electrical Insulating Products.
thermal degradation. It is possible that other factors, such as
Current edition approved Nov. 1, 2019. Published November 2019. Originally
moisture and vibration, will cause failures after the material
approved in 2014. Last previous edition approved in 2018 as D7894/
has been weakened by thermal degradation.
D7894M – 14 (2018). DOI: 10.1520/D7894_D7894M-19.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
3
Standards volume information, refer to the standard’s Document Summary page on Available from Institute of Electrical and Electronics Engineers, Inc. (IEEE),
the ASTM website. 445 Hoes Ln., P.O. Box 1331, Piscataway,
...
This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D7894/D7894M − 14 (Reapproved 2018) D7894/D7894M − 19
Standard Test Method for
Thermal Endurance of Coating Powders Used for Integral
1
Bus Bar Insulation Systems
This standard is issued under the fixed designation D7894/D7894M; 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.
1. Scope
1.1 This test method provides a procedure for evaluating thermal endurance of coating powders by determining the length of
aging time at selected elevated temperatures required to achieve dielectric breakdown at room temperature at a pre-determined
proof voltage. Thermal endurance is expressed in terms of a temperature index.
1.2 This test method is applicable to insulating powders used over a substrate material of copper or aluminum.
1.3 Units—The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated
in each system are not necessarily exact equivalents; therefore, each system shall be used independently of the other. Combining
values from the two systems is likely to result in non-conformance with the standard.
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, health, and environmental practices and determine the applicability of
regulatory limitations prior to use. Specific precautionary statements are given in Section 7.
1.5 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2
2.1 ASTM Standards:
D149 Test Method for Dielectric Breakdown Voltage and Dielectric Strength of Solid Electrical Insulating Materials at
Commercial Power Frequencies
D1711 Terminology Relating to Electrical Insulation
D5423 Specification for Forced-Convection Laboratory Ovens for Evaluation of Electrical Insulation
3
2.2 IEEE Document:
IEEE 101A Simplified Method for Calculation of the Regression Line
3. Terminology
3.1 Definitions—For definitions of terms used in this test method refer to Terminology D1711.
3.1 Definitions:
3.1.1 For definitions of terms used in this test method refer to Terminology D1711.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 thermal endurance, n—an expression for the stability of an electrical insulating material, or a simple combination of
materials, when maintained at elevated temperatures for extended periods of time.
4. Summary of Test Method
4.1 Specimens are aged in air at a minimum of three temperatures above the expected use temperature of the material. Exposure
to ambient stress conditions, followed by dielectric proof voltage tests in an electrically conductive solution, are periodically
1
This test method is under the jurisdiction of ASTM Committee D09 on Electrical and Electronic Insulating Materials and is the direct responsibility of Subcommittee
D09.01 on Electrical Insulating Products.
Current edition approved Nov. 1, 2018Nov. 1, 2019. Published November 2018November 2019. Originally approved in 2014. Last previous edition approved in 20142018
as D7894/D7894M – 14.D7894/D7894M – 14 (2018). DOI: 10.1520/D7894_D7894M-14R18.10.1520/D7894_D7894M-19.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
3
Available from Institute of Electrical and Electronics Engineers, Inc. (IEEE), 445 Hoes Ln., P.O. Box 1331, Piscataway, NJ 08854-1331, http://www.ieee.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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D7894/D7894M − 19
conducted to determine the time of aging at each elevated temperature required to reduce the breakdown voltage to a pre-selected
percentage of the original breakdown value. These thermal life values are used to construct a thermal endurance graph by means
of which it is possible to estimate a te
...
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