异步电动机定子绕组的故障诊断方法

Method for Diagnosing the Stator Winding Faults in Squirrel Cage Induction Motor

为及时发现并排除电动机的早期故障,保障电机设备的安全运行,提出利用失电残余电压诊断异步电动机定子绕组匝间短路故障的新方法并讨论了诊断匝间短路故障多种特征量的有效性;分析电动机失电后的残余电压并讨论了完好电机与故障电机残压中的频率成分。通过分析残压中高次谐波成分的变化可诊断定子绕组匝间短路故障;同时根据匝间短路故障后,完好相与故障相端电压所含谐波成分的不同,可确定故障发生的位置。实验证明该法对供电电源不对称及负载的波动具有鲁棒性,同时可诊断绕组早期轻微匝间短路故障。

The MCSA-based techniques for inter-turn stator fault detection have been reported, almost of these techniques are based on the analysis of low-or high-frequency components, which are produced by the inter-turn stator faults. However, the physics behind the existence of such components are not clearly explained, also, issues such as voltage unbalance, constructional imperfections that produce similar effects are not addressed. Considering the aforementioned factors, a new approach is proposed to detect the stator winding inter-turn short circuit fault in squirrel cage induction motor by the residual voltage after AC dump. Through analyzing the reason of residual voltage, the harmonies of residual voltage in the stator winding were compared between healthy and unhealthy motor. When a few turns of a stator phase are short circuited, they get isolated from the balanced three-phase winding set and act as a pick-up coil to these harmonies irrespective of their pole pair numbers. As current flows in the shorted turns, these harmonics will be induced in the healthy portion of the winding. Since the mutual inductance between the shorted turns and the three phases are different, it will also be able to detect the faulty phase unequivocally. By thoroughly analyzing the changes of higher harmonic in the residual voltage after AC dump, the detection and location of inter-turn short circuits in the stator windings were made. One of the key problems is to establish the fundamental frequency of the residual voltage, the FFT-FS spectrum zooming method was adopted. The scheme is largely insensitive to the supply voltage and the fluctuation of load, also, it can diagnose an early fault of the stator winding. The experimental results demonstrate that the method is valid and effective.