Vector control of the linear asynchronous motor

IV SUMMARY PhD Thesis VECTOR CONTROL OF THE LINEAR ASYNCHRONOUS MOTOR Hüseyin ALTUN Fırat University Graduate School of Natural and Applied Sciences Department of Electrical and Electronics Engineering 2001, Page : 132 In this thesis, the mathematical model of a vector controlled linear asynchronous motor has been obtained using quasi one dimensional magnetic field approach. In this mathematical model, longitudinal end effect, transverse edge effects, skin-effect and saturation due to the non linear characteristic of the magnetic material have been all taken into account. For this purpose, a literature search has been done in order to find out the application areas of the linear motion electromagnetic systems. It has been found that, the quasi one dimensional field approach which is a direct magnetic field analysis method is convenient for the double-sided linear asynchronous motor which is already present at Fırat Unv, Department of Electrical and Electronics Engineering machines laboratory. First by making some assumptions, one dimensional partial differential equation governing the system has been obtained. For the solution of this partial differential equation, in steady state, by taking end-effect into account an equivalent goodness factor has been calculated which is determined from the equivalent air gap, electrical conductivity and the thickness of the secondary.Then, from the calculations of the power and thrust in the magnetic field, the equivalent circuit parameters have been obtained for different speed and frequencies. Theoretical results of the model have been compared with the experimental results for steady state. The accuracy of the theoretical results has been verified by comparison with experimental results for a test motor. Good agreement is demonstrated. The percentage error between the theoretical and experimental results varies from 5% to 10%. The linear asynchronous motor which is different from its rotary equivalent, has been simulated by using vector control schemes. Since the motor has a topological structure different from that its rotary counterpart, the parameters of the equivalent circuit modeling the linear asynchronous motor varies with both frequency and speed. The effect causes these variations is called the end-effect, which reduces the conventional magnetic field in the air gap and so the overall performance of the motor. Hence, this effect which causes the parameters variations has been taken into account in the mathematical model of the motor. Contrary to the design of current, speed and magnetic field controllers for the rotary motor, the controllers have been designed, for the simulation by using the changing equivalent circuit parameters of the linear motor. In this study, Matlab/Simulink program has been used for obtaining the control results of the simulation. For better accuracy, instead of using look-up tables to compensate for the changing variables, a computer program has been developed in Matlab program editor which computes the speed and frequency dependent variables on-line with the program developed by using toolboxes in Matlab/Simulink program. Key Words : Linear Induction Motors, Linear Electrical Machines, Vector Control