Research On Electromagnetic Force Of Linear Induction Motor

As the rotor of linear induction motor is of such some characters as cut-off ends, big air-gap length, and so on, its performances are largely different from general rotating motor even if they are of the same working theory, efficiency, power factor and starting performance are all much lower than general rotating induction motor. But the linear induction motor has many advantages such as simple structure, high mechanic reliability, high control accuracy, directly driving linear motion, and so on, which make linear induction motor to be wide use in many fields, especially in Urban traffic system. Linear induction motor will play a great important part in traction, and absolutely replace the rotor induction motor. In this paper, more attention is paid to the analysis on electromagnetic force and the characteristics of the single-sided linear induction motor(SLIM).In this paper, firstly, theoretical analysis on all kinds of end-effects of SLIM is given. Based on the 'Full filled slot' and 'half filled slot' of first slot winding, the thesis carries out the air-gap flux and core-yoke flux. Then, the working theory of the longitudinal dynamic end-effect and horizontal end-effect of the SLIM are analyzed in detail, and their function factor are carried out in the result. After that, the SLIM T type equivalent circuit model with end-effects is established. The thesis carries out the analysis on SLIM's air-gap flux, as a result, the analytic expressions of the SLIM's electromagnetic force: thrust force and levitation force, efficiency and power factor are derived. The change curve of SLIM's thrust force, levitation force, efficiency and power factor with the different current and its frequency, air gap, secondary structure and velocity is calculated by the Matlab simulation.Because the magnetic field of SLIM is a kind of non-symmetrical vortex field, it can't accurately be solved with the traditional analytical method. In this paper the three-dimensional magnetic field is translated into two-dimensional magnetic field, and the two-dimensional nonlinear electromagnetic field of SLIM is numerical computed by using the finite element method. Based on this theory, the transient characteristics of single-sided SLIM are simulated and analyzed by using Ansys which is a sort of special software for the finite element analysis of electromagnetic field. The distributing of the magnetic field, the curve of thrust, levitation force and flux density of the air-gap are gotten with the different parameter. The contrative results show that the theoretical analysis is correct.