Mathematical model and vector control of a six-phase linear induction motor with the dynamic end effect

Abstract

This study investigates a short primary double-side six-phase linear induction motor (LIM) operating in non-periodic transient conditions. The main purpose is to solve the problems arising from the dynamic end effect. The equivalent circuit method is used for intensively studying the transient time-varying law of eddy current and excitation inductance, and the finite element method is adopted for verification. The calculation of eddy current loss leads to an expression of secondary equivalent resistance. Then, a mathematical model is established for the six-phase LIM involving the dynamic end effect. Furthermore, the matrix reconstruction method is adopted for the coupling of windings. Based on the time-varying characteristics of the model, an improved vector control method that can update the velocity-related correction coefficients through on-line calculation is proposed. During the transient process, the slip frequency and the torque current are modified in real-time to achieve the maximum output thrust of the motor. This approach can compensate for the thrust drop caused by the dynamic end effect, thereby improving the control precision. Simulations and experiments show that the related theory and the proposed control method are feasible and effective.