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

The continuous progress in electronic switches employed in electronic drives has brought higher performances and, potentially, new problems especially from the electric motor insulation systems point of view. In fact the PWM inverter waveforms, characterised by voltage drops at high frequencies, can influence the lifetimes of these insulating systems in a different way with respect to the traditional sinusoidal voltages. In this work the behaviour of enamelled copper wires subjected to quasi-square voltages is studied, particularly the attention is focused on the influence of the voltage rise time on the ageing process. Partial discharge (PD) monitoring during the tests enables us to explain the obtained results