Design And Study Of Novel Permanent Magnet Disk Coreless Motor Based On Halbach Array

The coreless disk permanent magnet (PM) synchronous machine which has themerits of short axial dimensions, light weight, compact structure, small moment ofinertia, small electrical and mechanical constants can be made into a multiple airgaps composite structure and widely used in thin installation required equipmentsuch as electric vehicles, robot, robot mechanical arms and household electricalappliances. The coreless disk PM machine has a variety of combination style, and thedual-outer-rotor and inner stator structure is further studied in this paper.Firstly, in order to make full use of the space of the outside diameter of the motor,the wedge air-gap structure based on Halbach array is proposed in this paper. A250W coreless disk PM synchronous machine is designed, and the calculationmethods of machine rotor poles, pole arc coefficient and conductor duty ratio arepresented. The motor is spread circumferentially to obtain the2D model, and the2Dmagnetic field is calculated using the finite element method.Secondly, the air domain problem of open domain field is analyzed in the3Dsimulation, and influence of the value of the air domain on air-gap flux density isobtained. In addition, the model with appropriate air domain size is established, Andradial distribution of the air-gap flux density is analyzed. The machine rotor structureis optimized mainly in magnetization direction of Halbach permanent magnet array,permanent magnet thickness, and permanent magnet width. The new structure rotorswhich have different thickness and width PMs are proposed. In order to get theadvantages and disadvantages of each structure, sinusoidal degree of thecircumferential air-gap flux density, harmonic content of the air-gap flux density, anddistortion rate of the no-load voltage are calculated and compared. Based on theproperties of permanent magnet rotors, the trapezoidal structure disk permanentmagnet motor is proposed in this paper. Finally, compared with other structures withthe same permanent magnet usage, the advantages of the trapezoidal structure diskpermanent magnet motor are obtained.Finally, the magnetic field of trapezoidal structure disk permanent magnet motor is analyzed. leakage magnetic coefficient of no-load is calculated using flux method,and electromagnetic torque characteristics of rated load is analyzed. Eddy currentloss of permanent magnet are calculated under no-load and rated load condition byfinite element method, and the main factors influencing eddy current loss areacquired. The d-axis and q-axis inductance of motor under conditions of differentloads are calculated, and axial electromagnetic force of motor is analyzed in thepaper. The relevant conclusions are obtained which can provide useful value for thefurther research of this kind of motor.