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Medium term aging characterization of enamelled for high frequency applications

This work is related to a medium term research program which aims at studying the behaviour of twisted pair specimens of enamelled copper wires subjected to high frequency sinusoidal voltage waveforms which are used in some advanced types of electrical machines. High frequency voltages due to, for instance, converter operation are not considered in this paper. The following test conditions were adopted: different voltage amplitudes up to 2 kV, selected voltage frequencies up to 5 kHz and test temperatures up to 200 /spl deg/C. The experimental work aims at defining reference-testing procedures and at studying the aging process of enamelled wires which are usually employed in random windings of electrical machines. As final result, a phenomenological model of the aging process, acting in the considered insulation system, is obtained and it is accurately defined on the grounds of the output data. The type of test method adopted and the type of data processing appear worthy to be used in order to characterize enamelled wires in terms of thermoelectrical degradation processes in presence of partial discharges.