Design Of A Wound Rotor For A Bearingless Induction Motor And Its Suspension Force Compensation

Utilizing the structure similarity between the magnetic bearing and the stator,a bearingless induction motor(BIM)is embedded with an extra suspension winding on the basis of the common induction motor that only has one torque winding,and by controlling the current in suspension winding and torque winding separately,the BIM can realize stable suspension and frictionless rotation.It has a broad prospect in the many special electric fields,such as aerospace,high-speed hard disk,flywheel energy storage,biological medicine,sterile and pollution-free operation.Considering the effects of induced current in the suspension winding,the motor iron core saturation and the cogging effects,a novel wound BIM is designed,the traditional mathematical model is optimized and the control system is improved in this dissertation.The main research contents are as follows:1.The research background of BIM is summarized and the present research status as well as its prospect are discussed.The BIM design idea,the suspension principle and the stable suspension conditions are explained.The general mathematical model of BIM was deduced by analytical method and an air gap magnetic field oriented control system was built based on this model,which brings the foundation for the subsequent research.2.Aiming at the influence of the induced current of suspension winding,a new type of wound rotor BIM is designed.The wound rotor uses a special structure to only induce the torque winding magnetic field.The results show that the designed new wound BIM can effectively suppress the induced current of suspension winding,eliminating its influence on the suspension force.3.Aiming at the problem that the accuracy of the traditional BIM mathematical model is affected by the magnetic saturation of the iron core of the motor and the cogging effect,a combination of Finite Element Method(FEM)and Least Squares Principle(LSP)is proposed.The non-linear model fitting method uses two-dimensional fitting for the suspension force,three-dimensional fitting for the unbalanced magnetic pulling force,and the original linear model is modified and optimized.4.Aiming at the influence of the armature reaction and the magnetic saturation in BIM,a compensation method for the phase and amplitude of the suspension force is proposed.The simulation results show that this method effectively suppresses the problem of displacement overshoot and reduces the fluctuation of the motor rotor during startup.5.The digital experiment control system is built and the motor rotation and rotor suspension experiments are studied.Experimental results show that the designed new wound BIM can not only obtain greater suspension force,but also effectively reduce the vibration of the rotor during startup and improve the motor suspension performance.