The PD and Endurance Features of Enameled Wires at Short Repetitive Impulsive Voltages

Partial discharge (PD) and endurance test under repetitive impulsive voltages are necessary for insulation systems of inverter-fed motors to guarantee its reliability. When performing partial discharge inception voltage (PDIV) and endurance test using impulsive voltages, the repetitive impulsive voltage parameters such as rise time, fall time, frequency and duty cycle could influence test result significantly according to our previous studies under repetitive square wave voltages with 50% duty cycles. However, there is little study on the influence of repetitive impulsive voltage with very short time duration, which is the real voltage stressed on insulation in stators, on PD and endurance. Therefore, this work focuses on the investigation of the effects of short unipolar repetitive impulsive voltages with 200 ns voltage duration on PD statistics and insulation lifetime of enameled wires. A great number of PD and endurance tests under impulsive voltages is performed on twisted wires used for inverter-fed motor insulation. Both ultra-high frequency (UHF) and ultraviolet sensors were used to suppress disturbance produced by power electronic devices and thus, receive PD signals with high signal to noise ratio. Experimental results show that PD magnitude under unipolar short impulsive voltages with different rise times increase significantly with the decreasing rise times, which is similar to the results obtained at bipolar repetitive square wave voltages with 50% duty cycles. Moreover, endurance test under two voltage conditions indicate that, even with same peak-to-peak value and frequency, short pulse voltages will give rise to longer endurance than square pulse voltages.