The Control Of Linear Induction Motor Based On Low-Speed Mag-Lev Vehicles

The linear induction motor is a transmission apparatus which transforms electric energy into mechanic energy directly. It possesses such advantages of simple structure, low noises and long durability, and it's easy to maintain. For these reasons, it is widely used in industrial field, especially used in the new transporting instrument—Magnetic Levitated Vehicles (MLVs) on railways. An MLV employs the magnetic force, enabling the vehicle to float over the rails, driven by linear electric motors. So there is no mechanical contact with the ground, no loss in friction, and it's easy to maintain and convenient to use. Thus, the study of the driven control of the linear inductive electric motors is of practical significance to the development and actual utilization of MLV technology in China.Firstly, the analysis of linear induction motor used in the maglev train is conducted. the expression of air gap magnetic field and magnetic force are derivatived, and the natural characteristics and the traction characteristics are elucidated in different situation, it shows the results of the simulation. Then, based on the research of control systems used in the LIM, the control way of constant current and constant slip frequency is established, and the results show that it can provide thrust force satisfactorily and at the same time avoid disturbance, generated by excessive fluctuation of nonnal force, on the levitation system. Magnetic flux linkage locus PWM control method is provided in detail. The control method is simulated at last. The results verify that the control way of constant current and constant slip frequency can provide constant thrust force in constant torque field, and keep slip rate constant in constant power field. The comparison between the simulation data and the theory results shows that the both are dovetailed in the error extension.