Research on testing system of partial discharge characteristics for mine motor based on high slope PWM pulse generator

Partial discharge seriously damages the operation of mine motors. Moreover, high slope (dV/dt) pulse width modulation (PWM) pulse is one of the most critical causes of partial discharge in motor windings. The reason is that with the development of power electronics technology, motor drives generally adopt frequency converters. However, the high-slope PWM pulse is generated in the motor winding and the inverter or cable when the inverter drive motor is running. Compared with power frequency ac voltage, the PWM pulse with high dV/dt is easier to generate partial discharge. Based on partial discharge detection and characteristic testing of mine motor, in order to simulate PWM pulse wave from frequency converter in mine motor, a pulse generator with high dV/dt is urgently needed for the signal injection of Cable Partial Discharge detection. However, the existing pulse generator for partial discharge testing cannot generate ultra-high dV/dt pulses with microsecond rising time. To address this problem, a new type of PWM pulse generator with ultra-high dV/dt output is designed. The pulse generator can emit the bipolar (±1.2 kV) pulse with the slew rate of (+50 kV/μs), and per unit polar output waveform can reach to 1.2 kV with the rising rate of 250 kV/μs. In this study, the partial discharge characteristic test of the coal mine motor was carried out by using the designed detection device, which proved the feasibility of the pulse generator for measuring the local test of the motor. The characteristics of partial discharge in the coal mine motor are further explored. Through the simulation test, the partial discharge characteristics of the tested analog motor winding sample is in the range of 12-19 GHz, and the center frequency is 15 GHz. © 2019, Editorial Office of Journal of China Coal Society. All right reserved.