DE-79-07-3 -- Laboratory Evaluation of Hermetic Motor Insulation PDF

Motor insulation materials and production methods are changing and will change more drastically in the future as a result of environmental protection requirements and energy conservation efforts. Faced with these changes, the hermetic motor application engineer needs definitive information about the thermal capability, chemical compatibility and life expectancy of new or modified insulation materials. Methods of evaluating hermetic motor insulation materials in refrigerant environments have been developed and are described. These include sealed tube tests using gas chromatography and mass spectrometry for analysis; aerosol tube tests for measurements of AC and DC conductance, dissipation factor and capacitance; and sealed glass electrical cell tests for long term aging with monitoring of changes in electrical properties. It is concluded that hermetic motor insulation materials must be evaluated in the approprlate refrigerant environment. Laboratory testing in air may lead to erroneous conclusions about insulation life and thermal capability of materials intended for refrigeration and airconditioning applications.