感应电机电源切换中残压和电压差的研究及最优切换策略

Residual Voltage, Voltage Difference and Optimal Switching Strategy During the Power Switching of Induction Motors

为了在不同备用电源下均能够尽可能地抑制感应电机电源切换中的冲击问题,有必要寻求最优电源切换方式,并在考虑开关动作时间下确定最有利切换时刻,为此,需要对断电后定子残压及其与不同备用电源间的电压差和相角差进行更加准确的定量研究。本文首先根据感应电机断电后的定子电流实测波形,发现电机断电后依次进入两个阶段——定子两相不对称瞬态和转子自由运动阶段,这种考虑必然提高定子残压的准确定量计算;然后,基于感应电机对称、不对称空间矢量模型,对断电过程两个阶段分别进行深入的解析推导,求得定子残压解析表达式;最后,重点研究定子残压及其与不同备用电源间的电压差和相角差特性,据此确定最优电源切换策略和最有利切换时刻,并通过感应电机电源切换实测结果验证了所得结论的正确性和可行性。

In order to suppress the inrush problems during the power switching of induction motor as much as possible under the different alternate power sources, it is necessary to select the optimal power switching method and determine the best switching moment with the consideration of the action time of the switch. Therefore, the stator residual voltage after the power off, the voltage difference and the phase-angle difference between the residual voltage and the voltage of the different alternate sources should be quantificationally researched more accurately. Firstly, it is found that there are two operation stages of motor based on the test wave of stator currents after the power off, that is, the short stator two-phase asymmetrical transient process and the rotor freedom operation. And the result approves inevitably the accurate quantitative calculation of the stator residual voltage. Then, the analytical derivation of two stages of the power-off process is made respectively in depth based on the symmetrical and asymmetrical vector models of motor. And the analytical expression of the stator residual voltage is obtained. Finally, the stator residual voltage, the voltage difference and the phaseangle difference between the residual voltage and the voltage of the different alternate sources are studied with emphasis. As a result, the optimal power switching strategy and the best switching moment are determined. And the drawed conclusions are verified to be correct and feasible by the test results of the power switching of induction motor.