Slot discharge pattern of 10 kV induction motor stator coils under condition of insulation degradation

In the manufacturing process of the 10 kV induction motors, a semi-conductive layer with certain resistance covering the linear part of the stator coil is often used to suppress the partial discharges (PDs) happened in the slot. However, due to electromagnetic force while the motor is running, slot discharge is still one of the main causes of stator insulation degradation. In this paper, an adjustable width mockup core slot is designed using silicon steel sheet. Several 10 kV real machine stator coils subjected to varying aging degrees are adopted as test coils. The phase resolved partial discharge (PRPD) patterns of slot discharge are analyzed using a PRPD analyzer and the variation law of slot discharge patterns with voltage variation is illustrated. The investigation result has been applied to the online monitoring and pattern recognition of the insulation for a 10 kV induction motor in a coal mine and it has great application significance.