Standard Historical Last Updated: Dec 11, 2013
ASTM D3145-08

Standard Test Method for Thermal Endurance of Electrical Insulating Varnishes by the Helical Coil Method

Significance and Use

This test method is used to determine the effect of exposure to elevated temperatures on the bond strength of combinations of magnet wire insulations and electrical insulating varnishes. The results are used as a guide for the comparison and selection of varnishes and combinations of varnishes and magnet wire insulation for specific applications. Test Methods D 1932, D 3251, and D 3850 describe additional tests for determining the thermal endurance of insulating varnishes. A comprehensive evaluation of thermal characteristics includes a comparison of the thermal endurance determined in these different ways.

This test method is useful for research and product qualifications purposes.


1.1 This test method covers the determination of the thermal endurance of electrical insulating varnishes alone or in combinations with magnet wire insulation. Changes in the helical coil bond strength are used as the test criteria. The coils are made from bare aluminum or copper wire, or from film- or fiber-insulated magnet wire.

1.2 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 a specific precautionary statement, see Section 7.

1.3 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.

Note 1—There is no similar or equivalent IEC standard.

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Book of Standards Volume: 10.02
Developed by Subcommittee: D09.01
Pages: 3
DOI: 10.1520/D3145-08
ICS Code: 29.035.60