基于改进型相关算法的变频异步电机定子故障诊断

变频器供电下,异步电机定子电流谐波成分剧增,使定子匝间短路故障的诊断不同于电网直接供电。电网电压不平衡以及电机的先天不平衡也会影响诊断结果。针对以上问题,根据变频器调制频率构建参考信号,提出用改进型相关算法提取定子电流中调制频率基波成分,避开电网不平衡因素以及变频器高次谐波的影响,利用逆调制频率同步速变换将调制频率的基波正序分量转化为二倍频交流分量,将负序分量转换成直流量,通过对整周期采样长度取均值的方法将直流分量单独分离出来。并考虑电机先天不平衡因素定义了故障灵敏度因子。实验结果表明该因子能正确反映定子故障程度,消除了变频器的谐波成分和噪声对计算结果的影响,对供电电源不对称具备鲁棒性,方法有效可行。

Stator fault diagnosis in induction motor fed with variable converter via improved correlation algorithm

When induction motor is fed with variable converter, the harmonic components soared in stator current, and the di- agnosis of stator inter-turn short circuit fault is different from the case of direct power network. Furthermore, both the unbal- anced supply voltage sources and the inherent asymmetries in the motor will affect diagnosis. To solve the above problems, the reference signais are constructed by modulated frequency, and the fundamental component of modulated frequency in the stator current can be obtained accurately to avoid the influence of the unbalanced supply voltage and higher harmonic produced by con- verter. And the positive sequence component of modulation frequency is turned into the second harmonic by using synchronous speed transformation of the inverse modulated frequency, and the negative sequence one is transformed into the DC component. The DC component can be separated out by taking the mean algorithm applied to samplings of whole period. A sensitivity factor is defined to evaluate the severity extension of the inter-turn short circuit faults in the stator, which takes into account the man- ufactured asymmetry of the induction motor. Experiment results indicate that the sensitivity factor can accurately reflect the fault characteristics of the inter-turn short circuit, the influences of harmonics and noise can be avoided, and the algorithm hasstrong robustness on the unbalance of supply voltage. This method is feasible.