1. 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.

2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.

ASTM Standards

D149 Test Method for Dielectric Breakdown Voltage and Dielectric Strength of Solid Electrical Insulating Materials at Commercial Power Frequencies

D374 Test Methods for Thickness of Solid Electrical Insulation

D580 Specification for Greige Woven Glass Tapes and Webbings

D1346 Test Method for Testing Electrical Insulating Varnishes for 180 C and Above

D1711 Terminology Relating to Electrical Insulation

D2518 Specification for Woven Glass Fabrics for Electrical Insulation

D5423 Specification for Forced-Convection Laboratory Ovens for Evaluation of Electrical Insulation

D6054 Practice for Conditioning Electrical Insulating Materials for Testing

IEEE Publications

IEC Publications

Keywords

dielectric strength; glass fiber fabric; thermal endurance; varnish;

ICS Code

ICS Number Code 29.035.60 (Varnished fabrics)

DOI: 10.1520/D1932-04

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