基于三线法的低压散绕变频电机绝缘短板判定方法研究

Research on Judgment Method of Insulation Vulnerable Spot for Low-voltage Random-wound Inverter-fed Motor Based on Three-curve Method

低压散绕变频电机匝间绝缘的局部放电起始电压(PDIV)随脉冲电压上升时间变化而变化,导致现行标准难以发现上升时间变化时的绝缘系统短板。对此,考虑脉宽调制上升时间,联合重复脉冲和正弦电压下的PDIV测试技术,提出了确定低压散绕变频电机绝缘短板的三线法。首先,在正弦电压下测定主绝缘和相间绝缘PDIV,得到主绝缘和相间绝缘的PDIV最小值分布;然后,使用上升时间为50~200 ns的重复脉冲对低压散绕变频电机匝间绝缘进行PDIV测试,得到PDIV随上升时间变化的拟合曲线;最后,根据确定的三线图,考虑电机运行时上升时间,确定绝缘系统短板,并通过击穿实验验证三线法的可行性。结果表明:采用此方法可以对低压散绕变频电机绝缘短板进行判定,通过击穿实验验证了三线法的可行性。

The partial discharge inception voltage(PDIV) of the turn-to-turn insulation for low-voltage randomwound inverter-fed motor changes with the rise time of pulse voltage, resulting in that it is difficult to find the vulnerable spot of the insulation system when the rise time changes. Therefore, considering the rise time of pulse width modulation, we proposed a three-curve method to determine the insulation vulnerable spot of inverter-fed motors by combining the PDIV test technology under repetitive pulse and sinusoidal voltages. At first, the minimum PDIV distributions of main insulation and phase-to-phase insulation were obtained by testing their PDIV under the sinusoidal voltage. Then, the turn-to-turn insulation of inverter-fed motor was conducted PDIV tests using the repetitive pulse voltage with 50-200 ns of rising time, and the fitting curves of PDIV with rising time were obtained. At last, according to the three-curve diagrams, considering the rise time of motor, the vulnerable spot of insulation system was determined, and the feasibility of three-curve method was verified by breakdown experiment. The results show that the insulation vulnerable spot of low-voltage random-wound inverter-fed motor can be judged by the three-curve method, and the feasibility of the three-curve method is verified by breakdown test.