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Significance and Use
5.1 This test method is useful in determining the thermal endurance characteristics and thermal indices of film-insulated round magnet wire in air (see 1.3) (see Test Method D3251). This test method is used as a screening test before making tests of more complex systems or functional evaluation. It is also used where complete functional systems testing is not feasible.
5.2 Experience has shown that film-insulated wire and electrical insulating varnishes or resins can affect one another during the thermal exposure process. Test Method D3251 provides indications on the thermal endurance for a combination of insulating varnish or resin and film insulated wire. It is possible that interaction between varnish or resin and film insulation will increase or decrease the relative thermal life of the varnish and film insulated wire combination compared with the life of the film insulated wire tested without varnish.
5.3 The conductor type or the surface condition of the conductor will affect the thermal endurance of film-insulated magnet wire. This test method is used to determine the thermal endurance characteristics of film insulation on various kinds of conductors. The use of sizes other than those specified in 7.1.1 is permissible but is not recommended for determining thermal endurance characteristics.
5.4 The temperature index determined by this test method is a nominal or relative value expressed in degrees Celsius at 20 000 h. It is to be used for comparison purposes only and is not intended to represent the temperature at which the film insulated wire could be operated.
5.5.4 In most laboratories, the number of thermal endurance ovens is limited and, therefore, many different sets of specimens are thermally exposed in the same oven. All specimens are not necessarily removed each time the oven is opened. This extra temperature cycling will possibly have a degrading influence.
1.1 This test method covers determination of the thermal endurance of film-insulated round magnet wire in air at atmospheric pressure. It is not applicable to magnet wire with fibrous insulation, such as cotton or glass.
1.2 This test method covers the evaluation of thermal endurance by observing changes in response to ac proof voltage tests. The evaluation of thermal endurance by observing changes in other properties of magnet wire insulation requires the use of different test methods.
1.3 It is possible that exposure of some types of film insulated wire to heat in gaseous or liquid environments in the absence of air will give thermal endurance values different from those obtained in air. Consider this possibility when interpreting the results obtained by heating in air with respect to applications where the wire will not be exposed to air in service.
1.4 It is possible that electric stress applied for extended periods at a level exceeding or even approaching the discharge inception voltage will change significantly the thermal endurance of film insulated wires. Under such electric stress conditions, it is possible that comparisons between materials will also differ from those developed using this method.
2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.
D1676 Test Methods for Film-Insulated Magnet Wire
D1711 Terminology Relating to Electrical Insulation
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
Other StandardsIEC 60172 Statistical Analysis of Thermal Life Test Data Available from International Electrotechnical Commission (IEC), 3 rue de Varemb, Case postale 131, CH-1211, Geneva 20, Switzerland, http://www.iec.ch. IEEE 101 Statistical Analysis of Thermal Life Test Data 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.
ICS Number Code 29.060.10 (Wires)
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ASTM D2307-07a(2013), Standard Test Method for Thermal Endurance of Film-Insulated Round Magnet Wire, ASTM International, West Conshohocken, PA, 2013, www.astm.orgBack to Top