重复脉冲电压上升时间对变频电机绝缘局部放电起始电压影响研究

Influence of Repetitive Impulse Voltage Rise Time on Partial Discharge Inception Voltage of Inverter-fed Motors Insulation

重复脉冲电压下绝缘局部放电起始电压(PDIV)测试是评估低压变频电机绝缘性能的主要手段。为得到客观的PDIV测试结果,必须研究重复脉冲参数对PDIV的影响规律。利用重复脉冲电压下的局部放电测试系统,研究了20 ns、40 ns、60 ns和1μs 4种上升时间下变频电机匝间绝缘PDIV的统计特性。结果表明:重复脉冲上升时间处的过电压是PDIV测试结果偏高的主要原因,20 ns上升时间下测得的PDIV比基本无过电压的重复脉冲PDIV测试结果高约30%,这是因为持续时间较短的过电压幅值虽超过了实际PDIV,但由于缺少激发电子崩的初始电子,未发生局部放电。在对变频电机绝缘进行PDIV测试时,应充分考虑重复脉冲上升时间处过电压对测试结果的影响。

Partial discharge inception voltage（PDIV） tests under repetitive impulse voltages are the main means to evaluate the insulating properties of low voltage inverter-fed motors. In order to obtain the objective test results of PDIV, the effect laws of repetitive impulse parameters on the PDIV should be studied. The PDIV statistical characteristics of the turn-to-turn insulation of inverter-fed motors under four repetitive impulse voltage rise time, including 20 ns, 40 ns, 60 ns, and 1 μs, were studied by partial discharge（PD） test systems. The results show that the overvoltage at repetitive impulse voltage rise time is the main reason for the higher test results of PDIV. The PDIV obtained under 20 ns of rise time is 30%higher than that obtained under the repetitive impulse basically without overvoltage. This is because although the overvoltage amplitude with shorter duration time exceeds the actual PDIV, the partial discharge does not happen due to lack of initial electrons for exciting electron avalanche. When we evaluate the PDIV of inverter-fed motors insulation, the effects of the overvoltage at repetitive impulse voltage rise time on the test results should be fully considered.