Design And Optimization Of Novel Direct-Drive Permanent Magnet Synchronous Motor With Toroidal Windings

Direct-drive permanent magnet synchronous motor(PMSM)has advantages of simple structure,large torque and high power density,and is widely used in electric vehicles,industrial robots and aerospace fields.Due to the limitation of space position and installation size,some industries require the PMSM has the characteristics of larger torque and small volume.Based on the research of the traditional direct-drive PMSM and the direct-drive PMSM with toroidal winding,this paper proposes a novel direct-drive PMSM with toroidal winding(NTWDDPMSM)by changing the winding connection of the motor to further improve the torque density and other performance indexes of the motor.The structure of the proposed motor is introduced and its operating principle is analyzed.Moreover,some key technologies of the NTWDDPMSM are studied,such as the electromagnetic design,characteristic analysis,cogging torque minimization,and multi-objective optimization.Main research contents of this paper are as follows.1.This paper proposes an NTWDDPMSM,in which the characteristics of the winding connection are elaborated.And the operating principle is analyzed to explain the magnetic poles of the armature magnetic field doubled.Furthermore,the main structural parameters are designed.2.Based on the same electrical load,magnetic load and permanent magnet usage,the electromagnetic characteristics of the motor with different winding connections,which includes the conventional direct-drive PMSM(CDDPMSM),conventional direct-drive PMSM with toroidal winding(CTWDDPMSM)and NTWDDPMSM,are studied.The no-load air-gap magnetic flux density and no-load back-electromotive force(EMF)are analyzed for three motors.And some performances of the three motor,including torque,current,efficiency and power factor,are compaed.The comparisons show that the NTWDDPMSM has the merits of small volume,high torque density,large torque constant and so on.3.The cogging torque of the NTWDDPMSM is optimized by shifting magnetic poles of the motor and the effect of magnetic pole deviation on the motor performances is analyzed.According to the structural characteristics of NTWDDPMSM,the expression of cogging torque is derived and the angles shifted magnetic poles are calculated.Then,the finite-element model is established to study the influence of magnetic pole deviation on the performances of NTWDDPMSM,including the cogging torque,torque ripple,no-load EMF and efficiency.The results indicate that the NTWDDPMSM after shifting magnetic poles(SMP-NTWDDPMSM)has lower cogging torque,smaller torque ripple,and better no-load EMF waveforms,compared with the original motor.4.Taguchi method is adopted to realize the multi-objective optimal design of the SMP-NTWDDPMSM.Taking the torque and efficiency improved and the torque ripple and the total harmonic distortion(THD)of electromotive force(EFM)reduced as constraints,some design parameters,such as the pole arc coefficient,permanent magnet magnetization height,air-gap length and slot opening width,are selected as optimization variables.The experimental orthogonal table is established according to the number of the optimization variables and their levels,and finite-element analyses are taken for the orthogonal table.After that,the best parameter combinations are gained by analyzing the influence of the factor level of the optimization variable on the optimization objective of NTWDDPMSM.The simulation result reveals that the overall performance of the motor is greatly improved after multi-objective optimization.5.The processing and assembly process of the NTWDDPMSM prototype are introduced and the test platform is built.Afterward,some parameters of output torque,output power and current are measured when the motor is operating at different conditions.Finally,the experimental results are compared with the ones obtained by the finite-element model.The comparisons show that the error between simulation and experiment is about 5%,which is within the allowable range the reasonable range.Therefore,the rationality of the proposed motor and the correct of the finite-element results are verified.