A Method of Evaluating Insulation Systems In Motors [includes discussion]

This paper gives a method of functionally evaluating insulation systems in 5-horsepower 440-volt 3-phase squirrel-cage motors. By this method it is possible to compare various insulating systems with acceptable standards in terms of the years of expected life at any selected operating temperature. A motor test station is described and a procedure is given for a test cycle involving periods of humidification and heat run. Various data on insulation systems under test are given as an example of what might be expected from this method.