Analytical Solution of a Fractional-slot Double-layer-winding Open-slot Vernier Permanent Magnet Machine with Tooth Tips

An analytical solution(ANA)for a fractional-slot double-layer-winding open-slot vernier permanent magnet(VPM)machine with tooth tips is presented.Magnetic vector potential equations are analytically solved using the technique of variable separation in four subdomains in a two-dimensional polar coordinate system.Based on the solved magnetic vector potential,the flux density distribution,torque,flux linkage,inductance,electromotive force(EMF)and power factor are analytically developed.An 18-slot/32-rotor-pole prototype is analyzed,and the results match well with the finite element analysis(FEA),which validates that the ANA consumes less time than FEA.Therefore,the tooth tips are optimized using the ANA to improve the average torque.Moreover,the ANA can be used to evaluate the demagnetization withstand capabilities of permanent magnets.The material utilization,slot-filling factor,EMF,and torque are compared between the models with three and four subdomains.Finally,an experimental prototype is constructed and tested,and the results validate the ANA.

A high torque dual 3-phase permanent magnet vernier machine with strong fault-tolerance

The field modulation effect has been proposed and investigated in various electric machine topologies.Among them,permanent magnet vernier machines(PMVMs)have attained intensive research due to the high torque density and simple structure.However,the performance of PMVMs in terms of fault tolerance is seldom mentioned.This article proposes a novel dual 3-phase fault-tolerant PMVM with segregated concentric windings.Benefiting from the field modulation effect,the PMVM can generate high torque with low PM flux.The low PM flux also implies small fault currents in the short-circuit case.Therefore,the PMVM exhibits inherent good fault-tolerant capability without sacrificing torque performance.Two independent 3-phase modular winding sets are adopted to improve redundancy.To realize the physical and electrical isolation,each winding set is controlled by a standard 3-phase inverter.The healthy performance and fault tolerance of the proposed machine are evaluated by finite element analysis and verified by experimental tests.The results infer its advantages in healthy conditions and various fault scenarios,including open-circuit,short-circuit,and interturn short-circuit conditions.

Reduction of Unipolar Leakage Flux and Torque Ripple in Consequent-pole PM Vernier Machine

This paper proposes a new consequent-pole permanent magnet vernier machine(CPMVM),which can be regarded as a combination of two conventional CPMVM with opposite polarities.Based on the simplified axial magnetic circuit model,it is verified that the proposed CPMVM can reduce the unipolar leakage flux.In order to reduce the torque ripple of machine and improve the output torque of machine,the flux barrier is placed on the rotor of the proposed machine.Then,the parameters of the proposed CPMVM are optimized and determined.Moreover,the electromagnetic performance,including no-load air-gap flux density,average torque and torque ripple,flux linkage,back-electromotive force,cogging torque,average torque,torque ripple,power factor and loss,is compared with conventional surface-mounted permanent magnet vernier machine(SPMVM)and CPMVM.Finally,it is demonstrated that proposed CPMVM with flux barrier can effectively reduce the unipolar leakage flux and greatly reduce the torque ripple of machine.Also,compared with the SPMVM,the proposed CPMVM with flux barrier saves more than 45%of the permanent magnet material without reducing output torque.

Modeling and Analysis of Spoke-Type Permanent Magnet Vernier Machine Based on Equivalent Magnetic Network Method

In this paper,a new equivalent magnetic network(EMN)model is established for a spoke-type permanent magnet(PM)vernier(PMV)machine.Two different modeling methods are proposed for different parts of the PMV machine,considering that their magnetic field distributions are quite different.Hierarchical modeling method is proposed for the modeling of the rotor as the magnetic intensity of the rotor iron core presents gradient distribution along the radial direction.Mesh based reluctance network method is used for the modeling of flux modulation poles with irregular and unstable magnetic field distributions.Moreover,accurate PM leakage permeance calculation formulae are deduced to improve the simulation precision.The electromagnetic parameters,such as flux linkage,back electromagnetic force,electromagnetic torque and iron loss are predicted by the proposed EMN model.Finally,finite element analysis(FEA)and experimental results are given to verify the effectiveness of the proposed methods.

Magnets Shifting Design of Dual PM Excited Vernier Machine for High-torque Application

In this study,a novel dual permanent magnet excited vernier machine(DPMEVM)with magnets shifting in stator is proposed.Compared with the conventional permanent magnet synchronous machine(PMSM),the DPMEVM based on the bidirectional field modulation effect can operate in a wider torque range.However,the torque ripple of a conventional DPMEVM is high because of the superposition of the torque generated by the stator-side and rotor-side PMs.Consequently,a novel DPMEVM with magnets shifting is proposed to further reduce the torque ripple.First,the topologies and working principles of the baseline machine and proposed machines are introduced.Second,the torque-contribution harmonics are analyzed and calculated using the Maxwell tensor method.The calculation results reveal that the DPMEVM,benefiting from multiple working harmonics,can offer an enhanced torque capability compared to the PMSM.In addition,the torque ripple characteristics of the proposed machines are analyzed.It is verified that the torque ripple can be significantly reduced through magnets shifting.Third,the performances of the baseline machine and proposed machines are analyzed and compared in terms of flux density,open-circuit back-EMF,and torque characteristics.In addition,the proposed principle can be extended to machines with the same unit motor.Finally,a 120s-110p prototype machine is manufactured for validation.