Effect of Jump Voltage and Rise Time on the Temperature and Electric Field Distribution Along the Stress Grading System of An Inverter-fed Motor

This paper first built an inverter circuit which can change the number of cascaded units to obtain different multi-level voltage waveforms, such as 7-level, 9-level, etc. Secondly, a 2D axisymmetric model of the stress grading system of an 18kV inverter-fed motor was established, whose stress grading system includes the conductive slot coating and stress grading coating, named low resistance (LR) and high resistance (HR), respectively. A series of coupled electro-thermal simulations were carried out. The maximum electric field distribution, the average loss density, and the steady-state temperature rise along the low resistance and high resistance under different multi-level voltages were conducted, further, the influence of the rise time on the maximum electric field and temperature rise along the stress grading system was evaluated. The results show that when the jump voltage or the rise time increases, the maximum tangential electric field and the temperature rise on the low resistance is higher with the rise time increases while those of high resistance show a little increasing trend.