A dynamic test procedure for the evaluation of magnet wire insulation systems used in windings of electronic transformers having crossed turns

The test procedure discussed in this paper is considered to be a dynamic test of magnet wire insulation systems since the test specimens are subjected to the same environments that the products would experience during production. It was developed to make a quick test involving a number of variables so as to make a value judgment with confidence. The various NEMA standards for enameled or film insulated magnet wire contained various tests to be applied to the insulation while on the wire. These standards also refer to the IEEE Test Procedure for the "Evaluation of the Thermal Stability of Enameled Wire," No. 57, which embodies a twisted pair test specimen because it "simulates to some extent the actual use of the enameled wires in electrical equipment." Since most insulating systems are impregnated or dipped in an electrical insulating varnish, the procedure recommends that the test specimens "also be impregnated in an appropriate electric insulating varnish to simulate as closely as possible the actual insulating structure" and suggests that the varnish be cured. NEMA has recommended that unvarnished samples be used, since magnet wire manufacturers do not control the kind of varnish used in treating windings. These are static tests made on defined specimens under standard conditions to compare products.