Research On A Single Winding Bearingless Permanent Magnet Slice Motor

The bearingless PM slice motor utilizes the bearingless technology to realize the radial suspension, and achieves the suspension of the other 3 freedom degrees by the reluctance force. It has good performance including dependable capability and has high efficiency on axis direction and so on. It is a new high-integration magnetic suspension motor which has a good application prospect in the fields of ultra-pure driving including biochemistry, medical treatment and semiconductor industry and so on.The former prototype of bearingless PM slice motor utilizes two windings to drive the rotation and suspension. It has disadvantages including complex structure, serious flux leakage, and reduced dependability due to feasibility of short circuit between two windings. In this paper, a bearingless PM slice motor based on the single-winding structure is researched. It utilizes only one winding to realize the rotation and suspension together, and compensates for the above shortcoming of the dual-windings bearingless PM slice motor.In this paper, the basic principle and realization of the single-winding bearingless PM slice motor is researched. First, a concept of current components superposition is proposed, that is, winding current is considered to be made up of two components including torque component and suspension component, then the suspension force and torque model based on the three-phase restrict of the current components are deduced , and corresponding control strategy is introduced on this basis. Second, the universal model of the suspension force and torque in the motor is deduced when each winding current is considered as a free variable, because the addition of each phase current in the single winding bearingless PM slice motor dispense with the zero, and then, the winding current model and control strategy is researched based on the universal model with power optimal constraint in each winding. Then fault-tolerant capacity based on the universal model of the suspension force and torque is researched when one of the windings is disconnected, and the fault -tolerant model is deduced and the corresponding control strategy is also introduced. The above three mathematical model are proved by finite element analysis.According to the characteristics of single-winding structure, a new power system design based on the H bridge power topology is used, the hardware and software system of the digital signal processor (DSP) are also designed, based on above, a prototype of single winding bearingless PM slice motor is designed and produced. A series of suspension experiments are operated on the prototype motor to validate the control strategies researched in this paper. Experiment results show that the prototype motor can be suspended at 5 freedom degree and operate when one of the windings is disabled.