说明：  感应电机模型，利用simulink的simpower模块搭建，与论坛中千篇一律的传递函数搭建不同，直观明了，利用simulink搭建等效电路
(Induction motor model, use Simulink simpower module structures, the transfer function of the monotony of the Forum to build and intuitive to understand, the use of Simulink to build the equivalent circuit)