SiC逆变器供电的牵引电机匝间绝缘性能评估

Evaluation on performance of turn-to-turn insulation for traction motor powered by SiC inverter

采用碳化硅(SiC)逆变器供电,虽然可以减小牵引变频电机体积、质量、温升,提高电机效率,但逆变器输出电压的高频、短上升时间等特性给牵引变频电机绝缘带来了挑战,尤其是匝间绝缘将会承受更高的电压负荷,导致绝缘过早失效。本文首先通过模拟SiC逆变器在最大开关频率及实际电缆线长度下高压变频牵引电机匝间绝缘所承受的电压波形,在不同电压参数(频率、电压峰峰值、上升时间)、不同温度、不同匝间绝缘层厚度(0.23 mm、0.30 mm)下对高压变频电机电磁线进行局部放电起始电压测试及耐电晕寿命测试,并根据牵引电机的实际运行工况和绝缘系统的电负荷失效机理,分析PDIV、局部放电特性及寿命的变化机理。PDIV测试结果表明:频率与上升时间的变化并不会对PDIV产生影响;温度升高,PDIV呈现下降趋势,但由于制作工艺问题,在部分温度下会出现上升趋势;厚度的增加对PDIV提升较大,在考虑成本及效率可控的前提下,提高厚度能有效提高变频电机匝间绝缘能力。耐电晕测试结果表明:温度与上升时间的变化会造成绝缘寿命发生较大改变;频率及电压峰峰值对绝缘寿命的影响呈非线性关系,可用反幂模型表达,并且在工业应用上针对频率对绝缘寿命的影响可直接通过比例关系进行折算。

The use of silicon carbide(SiC)inverters for power supply can reduce the size,weight,and temperature rise of traction inverter motors and improve the motor efficiency.However,the high frequency and short rise time of the inverter output voltage would bring challenges to the insulation of traction inverter motors.The turn-to-turn insulation will be subjected to higher voltage loads,which will lead to premature insulation failure.In this paper,the voltage waveforms of turn-to-turn insulation of high-voltage inverter traction motor were firstly simulated when the SiC inverter is at the maximum switching frequency and the actual cable length.The partial discharge inception voltage(PDIV)test and endurance life test were conducted on the electromagnetic wire of high-voltage inverter motor under different voltage parameters(frequency,voltage level,rise time),different temperatures,and different thicknesses of turn-to-turn insulation(0.23 mm,0.30 mm).Then according to the actual operating conditions of traction motor and the electrical load failure mechanism of insulation system,the change mechanism of PDIV,partial discharge characteristics,and life was analyzed.The PDIV test results show that the change of frequency and rise time has no influence on the PDIV.The PDIV derceases with the increase of temperature.However,due to the fabrication process,the PDIV increases at some temperatures.The increase in thickness has a greater increase in PDIV.Under the premise of controllable cost and efficiency,increasing the thickness can effectively improve the turn-to-turn insulation performance of inverter motors.Endurance test results show that the changes in temperature and rise time would cause large changes in insulation life.The effect of frequency and voltage level on insulation life is non-linear,and it can be expressed by the inverse power model.In industrial applications,the effect of frequency on the insulation life can be directly converted through a proportional relationship.