Basis Research On A Bearingless Switched Reluctance Motor

Because of similarity between the construction of a magnetic bearing and that of a switched reluctance motor (SRM) stator, a bearingless switched reluctance motor (BSRM) integrates the magnetic suspension winding into the same stator so that the rotor may suspend and rotate at one time. The bearingless technology has been applied to the switched reluctance motor, which could fully enhance its high-speed performance. Moreover, it also provides a new approach to solve the problem of switched reluctance motor's noises and vibration because it actively controls the radial displacement of a rotor. The dissertation focuses on mathematic models, control strategies of the torque and radial force, power converters and optimal winding arrangements and designs the experimental platform of a bearingless switched reluctance motor. Successful levitation operations are realized based on diverse control strategies.On the basis of research of the former achievements, the mathematic models are revised concerning the couple between radial forces. The new model solves the problems of subsidence at the crown of the inductance's curve.Based on the principle and mathematic models, three kinds of control strategies are designed. Firstly, aimed at the shortage of the existing method of calculating the current advanced angle, the control strategy of main winding square-wave current is improved. And the influences of different combinations of winding currents on radial force and torque are analyzed. Then a least magnetomotive force strategy is designed. The novel control strategy can decrease torque ripple and motor losses. Aimed at the problem of controlling instantaneous radial force difficultly after the motor speed increases, the control strategy of controlling average radial force and average torque is designed.The designed principle of winding converters is presented. Based on the principle and mathematic models, this dissertation analyzes the requirement of converters and offers the design principle of converters. In order to increase reliability and reduce cost, the asymmetry converter is applied to main winding and the three-phase half-bridge converter is applied to levitated winding. Then all kinds of work states and mathematical models of converters are expounded. Aimed at disadvantages of a levitated winding converter, the improved measure is taken that a three-phase four-leg converter substitutes the three-phase half-bridge converter.Winding arrangement of BSRM is researched. The influence of winding arrangement on the midpoint voltage is analyzed when regarding a motor, power converters and a control system as a whole. As a result, four kinds of optimized winding arrangements are given, which can balance two split capacitors'load of converters. Moreover, according to the influence of winding arrangements on the netrual leg of the three-phase four-leg converter, optimized winding arrangements which are fit for the four-leg converter are offered.According to control strategies, a digital control system for real-time control is designed based on DSP and CPLD and a lot of experiments are completed. The experimental results verify that the rotor shaft may be successfully suspended.