ASTM D3145 - 13

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

    Active Standard ASTM D3145 | Developed by Subcommittee: D09.01

    Book of Standards Volume: 10.02


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    ASTM D3145

    Significance and Use

    5.1 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 D1932 and D3251describe 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.

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

    1. Scope

    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 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 1There is no similar or equivalent IEC standard.

    1.3 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.


    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

    D618 Practice for Conditioning Plastics for Testing

    D1711 Terminology Relating to Electrical Insulation

    D1932 Test Method for Thermal Endurance of Flexible Electrical Insulating Varnishes

    D2307 Test Method for Thermal Endurance of Film-Insulated Round Magnet Wire

    D2519 Test Method for Bond Strength of Electrical Insulating Varnishes by the Helical Coil Test

    D3251 Test Method for Thermal Endurance Characteristics of Electrical Insulating Varnishes Applied Over Film-Insulated Magnet Wire

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

    International Electrotechnical Commission Publications

    IEC60216-1 Guide for the Determination of Thermal Endurance Properties of Electrical Insulation Materials (Part 1)


    ICS Code

    ICS Number Code 29.035.60 (Varnished fabrics)

    UNSPSC Code

    UNSPSC Code 31211707(Varnishes); 26121500(Electrical wire)


    DOI: 10.1520/D3145

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    ASTM D3145

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