重复短脉冲下相对湿度对变频电机绝缘局部放电及耐电晕寿命影响研究

Influence of Relative Humidity on Partial Discharge and Corona-resistant Lifetime Under Short Repetitive Impulsive Voltage for Inverter-fed Motor Insulation

在上升时间为10 ns、电压幅值为3.5 kV、频率为5 kHz的重复单极性短脉冲下,实验研究了相对湿度分别为30%、50%、70%、90%时变频电机匝间绝缘的局部放电及耐电晕特性。结果表明:随着相对湿度的增加,试样的耐电晕寿命逐渐缩短,局部放电幅值先减小至某临界值后明显增大。这是由于随着相对湿度增加,电荷驻留效应减弱导致局部放电幅值减小,但当湿度超过某临界值后,微水聚集增强了局部电场,局部放电幅值增加。同时,微水的附着使试样的介电常数增加,从而使气隙间电场强度增大,这可能是其耐电晕寿命缩短的原因。

The partial discharge and corona-resistant features of the turn-to-turn insulation of inverter-fed motor at different relative humidity conditions(30%, 50%, 70%, 90%) were studied under unipolar repetitive short impulse voltage with 10 ns of rise time, 3.5 kV of voltage amplitude, and 5 k Hz of the frequency. The results show that with the increase of relative humidity, the corona-resistant lifetime decreases gradually, while the partial discharge amplitude decreases to a certain value and then increases significantly. This is because with the increase of relative humidity, the resident effect of charge reduces, leading to the decrease of partial discharge amplitude. However, when the humidity exceeds a certain critical value, the micro-water would accumulate and enhance the local electric field, resulting in the increase of partial discharge amplitude. At the same time, the attachment of micro-water increases the dielectric constant of sample, leading to the increase of electric field intensity in the air gap, which may be the reason for the decrease of its corona-resistant lifetime.