Research On The Harmonic Pole Cutting Of The Surface-mounted Permanent Magnet Motor Rotor And Its Influence On The Cogging Torque

Permanent magnet synchronous motor has become more and more widely used due to its high efficiency,high power factor,and simple structure.It also puts forward higher requirements for motor design to acquire higher torque density and lower torque ripple.Shaping permanent magnet is a simple direct and effective method for optimizing the performance of surface-mounted permanent magnet motor.In this paper,the method of shaping pole and its influence on cogging torque are studied.And a nine-phase surface-mounted permanent magnet synchronous motor is taken as an example for analysis and calculation.A preliminary scheme including the basic structure,main parameters and motor materials of a 9kW permanent magnet synchronous motor is designed.Then a prototype of permanent magnet motor adopting eccentric pole was tested to verify the effectiveness of the scheme.In order to calculate the leakage inductance parameters of the stator windings of a nine-phase permanent magnet motor,the method of numerical analysis is adopted.The mutual leakage inductance between layers in the slot,the harmonic leakage inductance between two coils and the leakage inductance at the end of the slot are calculated by the layered method,the total inductance subtracting the fundamental inductance and the magnetic vector potential,respectively.Then the correlation matrix is introduced to calculate the leakage inductance parameters between phases.This method can be programmed uniformly,has strong adaptability,and improves the accuracy of calculation,providing basis for analyzing and controlling multi-phase motor.The permanent magnet thickness functions of the sinusoidal shape and sinusoidal shape with third harmonic injected are derived under two different magnetization manner.Then,a nine-phase surface-mounted permanent magnet synchronous motor with two types of permanent magnet shape is simulated.The air gap flux density,back electromotive force and electromagnetic torque were analyzed.By comparing the electromagnetic properties with the motor using the original permanent magnet shape,the relationship between permanent magnet shape and torque characteristics is explored,which provides reference for pole optimization.In order to study the influence of sinusoidal shape with third harmonic injected on the cogging torque,the permanent magnet synchronous motors which adopt different kinds of permanent magnet shape are analyzed using the energy method,respectively.The square of the equivalent remanent flux density was analyzed utilizing Fourier decomposition method.The Fourier decomposition coefficients mattering with the cogging torque are compared to obtain the effect of three kinds of permanent magnet shape on the cogging torque.By comparing the result of the finite element method,the correctness of energy method is verified.