Research on AC and impulse stress gradient of coronaless stator end-winding for 10kV explosion-proof motor

In this paper, the corona inception voltages in air gap between the adjacent stator end-windings of increased safety high-voltage (HV) explosion-proof motor were measured, and the corresponding electric field were calculated basing on the established model. Under ac and impulse test voltages, the voltage (or stress gradient) distributions along a grading coating of stator end-winding were measured and calculated respectively. The structure of stress grading coating suitable for both impulse and ac voltage tests were optimized. The impulse corona inception voltage on a grading coating was also measured. The measured and calculated results show that the critical air gap distance between the stator end-windings for 10 kV explosion-proof motor is 9 mm, and the maximum ac and impulse peak electric field are limited to 2-2.2 kV/mm. The ac and impulse corona inception voltage gradients along a grading coating of stator end-winding are 720 and 1350V/mm respectively.