Characterisation of insulated conductors for high frequency applications

Abstract

The activities of the preliminary stage of a mediumterm research program aimed at studying the aging processes in the wire insulation of electrical machines supplied by inverters are illustrated. The experimental work allowed to select reference testing procedures and produced the results of tests carried out on twisted pairs of enamelled wires at different temperatures, sinusoidal voltages and frequencies.While the research plan regarded such results just as reference for future comparison to the outcome of steep waveform voltage tests, the available data allowed also to formulate, with reasonable accuracy, a phenomenological model of the aging processes acting in the tested insulation. Such a model could facilitate the implementation of the above research program next stages and appears worth to be extended to real winding insulations.

Failure mechanisms of polyimide and perfluoroalkoxy films under high frequency pulses

“…For example, Guastavino et al 1 have shown that the number of aging cycles to breakdown for twisted pairs of magnet wire is independent of frequency from 50 Hz to 5 kHz. Cerutti et al 2 showed similar data from 1.5 to 5 kHz. Yin 3 , however, not only showed similar data from 200Hz to 5 kHz, but also discovered that the number of aging cycles to breakdown decreases with increasing frequency when frequency is beyond 5 kHz.…”

Enamelled twisted pairs specimens: quasi-square voltage rise time influence on life-tests values

“…It is possible to assume that the frequency influence on the ageing phenomenon keeps constant. In [5] the previous hypothesis was experimentally confirmed in a range of frequencies values lower than the range values considered in this work but in first approximation the assumption of constant frequency influence varying the voltage amplitude could be considered true also in the cases here considered. Therefore at different voltage amplitudes it is possible to write: Considering the PD activity, decreasing the rise time a decreasing of the PD repetition rate is expected because of the time lag [6]; besides increasing the voltage level the PD number increases.…”