变频电机用聚酰亚胺薄膜电老化特性研究

为研究变频电机用耐电晕型聚酰亚胺材料耐局部放电老化机理,采用电导电流法分别测量了普通聚酰亚胺薄膜(100HN)和耐电晕型聚酰亚胺薄膜(100CR)电晕老化前、经10kV/mm、20kV/mm电晕强度8h老化后的电老化阈值。结果表明,2种薄膜的电老化阈值随电老化强度的增加而减小,且耐电晕型薄膜的电老化阈值始终高于普通膜的阈值;在2种薄膜的空间电荷限制电流区内,耐电晕型薄膜的电流增长率较大,说明其中含有更多的浅陷阱,测试结果与其170°C下退极化电流测试结果一致。这些浅陷阱有效调节了聚酰亚胺薄膜中电场的分布,改善其耐电晕性能。

Study on Electrical Aging Characteristic of Polyimide Film Used in Frequency Control Motor

In order to study the partial discharge mechanism of polyimide film used in frequency control motor, the electrical conduction current of both DuPont common polyimide film (100HN) and corona-resistant polyimide film (100CR) was measured before and after 8 hours corona-discharge aging under 10 kV/mm and 20 kV/mm. The results show that the electrical conduction current of 100CR is about one order of magnitude larger than that of 100HN. Based on the space charge aging theory, the electrical degradation threshold is 40 kV/mm for 100CR and 35 kV/mm for 100HN before corona-discharge aging and decreases with increasing corona-aged field for the two films, but the electrical degradation threshold of 100CR is higher than that of 100HN in the space charge limited current area, showing that there are more shallow traps in 100CR than that in 100HN. By measuring the depolarization current of the two films at 170 C, it is observed that the space charge magnitude of 100CR is twice larger than that of 100HN and the decay of depolarization current of 100CR is faster than that of 100HN. Results also show that there are more shallow traps in 100CR than those in 100HN. The results just agree with those from the electrical conduction current measurement. Because the electrical degradation threshold is the value of electrical field which space charges are accumulated in insulation and space charge can distort the electrical field distribution, the corona-resistant ability of 100CR is superior to that of 100HN. At the same time, a large quantity of shallow traps can more effectively ameliorate the electrical field distribution of 100 CR than that of 100HN, which can more effectively modifies the resisting corona-discharge ability of 100CR than that of 100HN.