Characteristic Research on the Sensor for Inter-turn Partial Discharge Measurement of Inverter-fed Motor Winding

In this paper, the characteristics of a novel type of non-contact electromagnetic induction sensor suitable for inter-turn partial discharge (PD) detection under an induced impulse voltage were studied. Taking the flexible advantage of ferrum-based nanocrystalline alloy thin strip applied in the open magnetic core, the sensor was desigined to be sensitive for the detection of high frequency but low amplitude PD current signal, and had a flexible and thin framework based on consideration of the convenient arrangement at the limted air gapness between the adjacent end-windings of motor. Through the sensor equivalent circuit model established, the curve patterns of the sensor's amplitude gain in the frequency domain were obtained. The transfer characteristics of the sensor were studied by means of theoretical and simulated analysis. The sensor's amplitude performes a bell-shaped characteristic, and its maximum gain can reach 10kV/A at a frequency of about 55 MHz. The finally experimental results, obtained from a typical case of the inverter-fed traction motor windings with the inter-turn void defects, have indicated that the this sensor has a excellent performance in detecting response signal of possible inter-turn PD of motor.