高频脉冲下牵引电机绝缘的局部放电特性

变频牵引电机定子绝缘承受来自变流器的连续高压方波脉冲,可能导致绝缘过早失效,其老化机理与工频交流电压作用下差异很大。局部放电是导致变频调速牵引电机绝缘失效的主要原因之一。研究高频方波脉冲下的局部放电特性为牵引电机绝缘材料的改进和优化提供理论基础,试验分析了普通和聚酰亚胺纳米复合薄膜制成的电磁线寿命,结果发现纳米试样的寿命得到很大提高。针对普通和聚酰亚胺纳米复合薄膜研究了不同脉冲频率、上升时间和温度对放电起始电压、平均放电量和放电次数的影响。结果表明,频率的增加、上升时间的缩短和温度的增加加剧了局部放电活动,普通薄膜试样的局部放电活动更强,其原因是纳米粒子的添加导致纳米复合薄膜存在大量界面区和电导率增加,电荷的迁移速率增大,空间电荷累积效应减弱。

Partial Discharge Characteristics of Insulation Used in Inverter-fed Traction Motor Under High Frequency Impulse

Stator insulation in inverter-fed traction motors may prematurely lose its function due to continuous square impulses voltage of converters,whose insulation failure mechanism is different from that under power frequency AC voltage.Partial discharge(PD) is one of the key factors in insulation failure of inverter fed traction motor.To understand aging and failure mechanism of insulation material under high frequency impulse,and to provide a foundation for improvement of insulation material,we experimentally researched overvoltage at the end of motor and windings because of high frequency impulse,which would lead to partial discharge and accelerating aging on the insulation,and analyzed the life of the common polyimide and nanocomposite films.Moreover,the PDIV(partial discharge inception voltage),mean discharge quantity and discharge number were tested with different impulse frequencies,rise time,and temperature,respectively.Results show that PD activity are enhanced with increase of impulse frequency and temperature,as well as decrease of rise time.Furthermore,PD activity of common polyimide film is stronger than that of nanocomposite one.Because a lot of interface exists in the nanocomposite,conductance of nanocomposite film is larger than that of common one,transport speed is higher,and space charge effect of nanocomposite is reduced.