Turn-to-turn capacitance variations correlated to PDIV for AC motors monitoring

The paper deals with a new indicator for monitoring the turn-to-turn insulation aging of ac motors. Measurements of capacitance and Partial Discharge Inception Voltage (PDIV) were performed on a large number of twisted pairs of enameled wires between standard thermal accelerated aging cycles. A significant increase of the capacitances and a reduction of the PDIV were noted on all the samples for three different diameters of enameled wires. The correlation of the capacitance increase with the degradation of the insulation quality opens perspectives for preventive maintenance applications.