Study On Basic Theory And Experiments For Self-Bearing Induction Motor

The self-bearing induction motor, which combines function of induction motor and magnetic bearings, can provide both torque and radial suspension forces. The rotor of the self-bearing induction motor can rotate with no mechanical friction. In recent years, self-bearing motors have been developed for high-speed machine tools, turbo-molecular pumps, compressors, blood pumps and computer disk drives, and have provided realization methods for many special drives.The self-bearing induction motor is a strong-coupled, nonlinear, multi-variable complicated system. This dissertation focuses on the fundamental theory and experiments of self-bearing induction motor including mathematic models, flux oriented controller, speed sensorless technology and the digital control system design. The detail contents are as follows:Firstly, the principle of radial suspension force is expounded. The mathematic models of radial suspension forces and rotation part of the self-bearing induction motor are deduced. The correctness of suspension principle and mathematic models are verified by ANSYS software, which is finite element analysis software of electrical machines. In order to realize the decoupling control of torque and radial suspension forces for self-bearing induction motor, two control system based on rotor flux oriented control and air-gap flux oriented control are designed. The two control systems are simulated with Matlab/Simulink toolbox. Simulation results have shown that rotor can suspension steadily, torque and radial suspension subsystems can operate independently. According to the simulation results, the rotor flux oriented control and air-gap flux oriented control are compared and analyzed.Secondly, according to a model reference adaptive system (MRAS), a method for estimating the speed of sensorless self-bearing induction motor drives is proposed. The mathematic models of MRAS are deduced, and the speed sensorless flux oriented control system of self-bearing induction motor is constructed. Using Matlab/Simulink toolbox, the simulation model is established. It can be seen that the control system has good performance by simulation in different speeds.Finally, based on the principle of rotor flux oriented control, the digital control system is designed using TMS320LF2407A of TI Corporation, and the flowcharts of each functional block are presented. Based on the prototype of self-bearing induction motor, the digital control system is debugged and optimized. The experimental rig of digital control system is set up and is used to validate control strategy.