| Magnetic bearing is a new kind of electromagnetic bearing using the controllable magnetic forceto suspend the rotor in the middle of the stator, possessing the unique advantages of contact-free,no-wear, high speed, without lubrication that traditional bearing cannot substitute, and because ofthese advantages magnetic bearing is widely used in the high speed motor. This thesis combinesmagnetic bearing and switched reluctance motor(SRM), mainly studies high speed magneticsuspended SRM, following work is introduced:Some familiar structures of5degree of freedom magnetic suspended motor are introduced, andthe symmetrical3degree of freedom magnetic bearing is selected as the structure of5degree offreedom magnetic suspended motor. The configuration and working principle of the PM biasaxial-radial magnetic bearing is presented. The accurate magnetic circuit model is establishedincluding the leakage and soft magnetic material reluctance. A magnetic bearing is designed based onthe model and tested in the3D finite element simulation, the results show that the design parameter isrational and right. Rotor dynamic is analyzed in ANSYS. The first order critical rotate speed isdesigned far away from the motor’s working speed by adjust the shaft diameter and allocating theparts on the right positions. So the motor possesses good rotor dynamic in the whole speed range.The experiment platform is designed including the control system of the magnetic bearing andSRM. The static and dynamic suspending experiments are carried out, and the waves are given andanalyzed. The motor is working at36000rpm in the end.In order to restrain the rotor’s gyro effect at high speed, cross feedback is studied based on thedecentralized PID control. A forward path is added in the control loop, velocity and displacementcross feedback in applied in the control system. The simulation results show that rotor’s gyro effect isrestrained effectively by cross feedback and the system stability is enhanced. |
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