Research On Basic Characteristics Of A 12/8-pole Bearingless Doubly Salient Electro-magnetic Machine

As the core of the more electric aircraft,the internal start/generator should be able to work in hard environment with high temperature and high speed.The bearingless switched reluctance machine which has the advantages of simple structure and good fault tolerance is suitable for internal start/generator.However,the bearingless switched reluctance machine can only works in half of a period and requires complex full control rectifier circuit.In this paper,a new type of 12/8-pole bearingless doubly salient electro-magnetic machine which can realize full period generation with simplified control circuit is been introduced.The structure and suspension principle of the machine are introduced.Considering magnetic saturation and the edge of magnetic flux,the mathematical model of the motor is build by Maxwell Stress Method.The relationship between suspension force and suspension winding currents is verified by comparing with the results of the finite element analysis which confirmed the accuracy of the mathematical model.Using the finite element analyze to get electromagnetic characteristics at different working state of bearingless doubly salient electro-magnetic machine.The influence of suspension winding current on static magnetic characteristics,generating characteristics and motoring characteristics can be acquired.At the same time,the state of rotor eccentricity is simulated and the suspension force with displacement stiffness curve is obtained,which provides the foundation for the suspension force control.This paper also introduces the suspension control system which uses TMS320F2812 as the center of control.By processing the current signal of the suspension winding and the rotor displacement signal of the rotor,a variable PWM wave can be output which can realize the double closed-loop adjustment of displacement and current.Finally,the static suspension experiment is realized by software PID control.The shaft of the motor can return to the center of the air when the suspension force load is changed suddenly.The relationship between suspension force and suspension winding current is experimentally tested,and the correctness of the simulation is validated after compared with the results by the finite element analysis.