Electromagnetic Characteristics And Starting Stability Of High Speed Permanent Magnet Synchronous Motor

The high speed permanent magnet synchronous motor(HSPMSM)has the advantages of high efficiency,small size and high power density,which is widely used in centrifugal air compressors and blowers.According to the magnetic flux path,HSPMSM can be divided into the radial flux permanent magnet machine(RFPMM)and axial flux permanent magnet machine(AFPMM).Because the rated torque of the high speed motor is small,there are bearing preload torque and load torque when starting,which will make it difficult to start the motor.With the improvement of motor performance requirements,it is very important and urgent to conduct comprehensive research on electromagnetic torque and starting performance of high speed motors.This paper focuses on the electromagnetic performance calculation and starting control stability research of the HSPMSM.The specific contents include:1.The analytical model of armature reaction field and the permanent magnet magnetic field for the slotless ultra-high speed AFPMM was established,the harmonics of the permanent magnet magnetic field and the armature reaction field were analyzed,and the torque ripple was discussed.The model could consider the topological structure of permanent magnets and winding distributions,and reflect the pulsating component of electromagnetic torque,which provides a theoretical direction and a universal method for the electromagnetic design of slotless AFPMM.2.The electromagnetic properties of slotless and slotted ultra-high speed AFPMMs were compared and analyzed.Analytical models of the armature reaction field and permanent magnet magnetic field of the slotted AFPMM were established by using the subdomain method,and the electromagnetic torque of the motor was solved by the Maxwell stress method.The influence of stator without/with slots and air gap thickness on electromagnetic torque was discussed.It provides a theoretical basis for the structure design of the high speed AFPMM.3.The analytical solution of the rotor unbalanced magnetic pull(UMP)of the slotted high speed RFPMM was obtained by using the perturbation method.The model can consider the UMP of the rotor under various eccentric conditions,which lays a theoretical foundation for the study of the bearing-rotor system dynamics of the high-speed motor based on multi-field coupling.4.The judging method of the HSPMSM’s starting stability and the corresponding control strategy were given.The nonlinear dynamic equation of the HSPMSM starting was established,and the Lyapunov’s first method was used to determine the stability.On the basis of traditional V/f control,based on instantaneous power feedback,the electrical damping was introduced to eliminate the instability of the system.The above work has important guiding significance for the electromagnetic design and starting control of the HSPMSM.