Research And Optimization On Core Loss Of An Outer-Rotor Flux-Switching Permanent-Magnet Motor

Due to the excessive exploitation and consumption of petroleum,the issues of energy crisis and environmental pollution have become increasingly prominent.Therefore,the energy saving and emission reduction have turned into the tendency.Due to the advantages of no emission and fuel consumption,electric vehicles,such as electric tractors and electric cars,have attracted attentions.As the power source of the whole machine,the performances of the drive motor directly affect the quality of the vehicle.Due to the advantages of high torque density,high efficiency and simple structure,flux-switching permanent-magnet(FSPM)motor is recognized to possess a broad prospect in the electric driving field.However,due to the flux-modulation effect,much harmonics exist in the air-gap of FSPM motor,and the core loss is relatively high,which might cause the overheating of motor and the irreversible demagnetization of permanent-magnets.Therefore,it is of great significance to research the core loss of FSPM motor and its optimization methods.In this paper,the relationship between core loss and air-gap harmonics is explored based on the flux-modulation theory.Taking the key air-gap harmonics of core loss as direction,a new method to optimize the core loss of FSPM motor is proposed.This study is always focused on the air-gap harmonics,and the core loss of an outer-rotor flux-switching permanent-magnet(OR-FSPM)motor is researched.The main contents are as follows:1.The background and significance of this research are described systematically.The relevant researches of FSPM motor applied in the field of electric vehicle are introduced.The characterictic of high core loss of FSPM motor is highlighted.2.Based on the flux-modulation theory and the MMF/permeance function,the mechanism of the generation of air-gap harmonics of an OR-FSPM motor is analyzed,which provides a basic theory to derive the relationship between core loss and air-gap harmonics of the OR-FSPM motor.3.A core loss calculation method of the OR-FSPM motor is obtained by using Bertotti equation.The equations describing the relationship between core loss and air-gap harmonics of the OR-FSPM motor are deduced.The key air-gap harmonics of core loss of the OR-FSPM motor is determined by solving the equations,which provide a clear direction for optimizing core loss of the OR-FSPM motor.4.An optimization method for core loss of FSPM motor based on air-gap harmonics is proposed.In order to reduce the core loss of the OR-FSPM motor,the key air-gap harmonics are taken as the objective.Meanwhile,the sensitivity analysis method is used to select the parameters with high sensitivity to the key air-gap harmonics,and the response surface method is applied to optimize the key air-gap harmonics.In the optimization process,the air-gap harmonics is not only the objective,but also a key bridge connecting the parameters of the motor and core loss.5.In order to verify the effectiveness of the optimization method proposed in this paper,the main performances of the optimal motor are analyzed in detail,including magnetic flux distribution,back electromotive force,core loss,output torque,temperature and so on.6.The experimental prototype is processed.The performances of the prototype such as output torque and efficiency are tested to verify the rationality of the method proposed in this paper.