Electromagnetic Torque Analysis And Modeling Of High Power Density PMSM

With the development of many industrial fields,motors are required to have higher power densitiy.High power density Permanent Magnet Synchronous Motor(PMSM)has become the first choice in many industrial fields due to their compact structure and high electrical load and high magnetic load.The high power density PMSM often works under complex and variable working conditions,and the motor is in magnetic saturation state,which makes the nonlinear characteristic of the electromagnetic torque of the motor remarkable.The traditional permanent magnet motor torque model is building under a low-saturation motor,which is a linearized model of dq-axis decoupling.It is also considered that the motor parameters such as flux linkage and inductance are constant values.In the high power density PMSM,the permanent magnet and ferromagnetic material of the motor are susceptible to the load and temperature and cause saturation phenomenon,which causes the motor parameters changeable and the electromagnetic torque changing nonlinearly,so that the high power cannot be satisfied.For the calculation of electromagnetic torque of high power density PMSM,this paper carries out the following research on the above problems:(1)High power density PMSM often works under high load and high current operating conditions.Due to the strong magnetic field saturation,the nonlinear parameters and coupling of the motor are more obvious.In this paper,the mathematical model of PMSM,the linear model of PMSM under dq axis and the nonlinear model considering magnetic saturation and cross coupling are established.Lay the foundation for follow up research work.(2)High power density PMSM has high magnetic load and high current load.It needs to maintain good working characteristics on the basis of high power density.This paper introduces the design flow and magnetic field analysis method of high power density PMSM.The loss of the PMSM is calculated,and the correction method under the core saturation is proposed.(3)The electromagnetic torque of high power density PMSM is complicated and difficult to calculate due to the influence of magnetic circuit saturation and cross coupling.In this paper,the electromagnetic torque model is analyzed from the perspective of magnetic field.The stator and rotor magnetomotive force of PMSM are analyzed.The saturation coefficient is proposed by magnetic circuit calculation and the traditional linear torque equation is modified.(4)Using the above analysis method,using simulation software building a high-power density PMSM model,and the saturation characteristics of the magnetic circuit of the motor are verified.The inductance parameter of the magnetic circuit saturation is calculated by the method of freezing conductivity.Four types PMSM were built.The effects of inductance parameters on permanent magnet torque and reluctance torque were studied under the magnetic saturation of the built in PMSM.The electromagnetic torques of four motors were analyzed.Cogging torque and torque fluctuation;the saturation coefficient obtained by finite element simulation is compared with the saturation coefficient calculated by magnetic circuit to verify the accuracy of saturation coefficient.