New Topologies of High Torque Density Machine Based on Magnetic Field Modulation Principle

With the increasing demand for high torque density in motors,more and more new topologies emerge.Furthermore,the magnetic field modulation principle is widely concerned and has evolved into an effective analysis method for studying the new motor topology.This paper introduces the principle of magnetic field modulation.And the research on high torque density in recent years is reviewed from the perspective of magnetic field modulation,including permanent magnet vernier machine(PMVM),flux reverse machine(FRM),flux switching machine(FSM),dual permanent magnet(DPM)machine,and DC biased machine.The principle of magnetic field modulation makes it possible to propose higher torque density topologies in the future.

Torque Improvement of Spoke-type Permanent Magnet Motor with Auxiliary Stator Using Harmonic Current Control Strategy

The spoke-type permanent magnet motor with auxiliary stator exhibits high torque performance owing to the flux focus effects.To further improve its torque density,this paper proposes a control method by using harmonic current strategy.Based on the theoretical analysis,a 3-D torque look-up table by dq-axis current and electrical angle is established with the aid of the finite element method(FEM).The maximum torque per ampere curve at each rotor position is identified and summarized to adequately indicate the relationship between torque and current amplitude of the motor.Through theoretical derivation,it is concluded that the minimum torque cost curve is the contour line of?Te/?i2,which can be employed to identify the harmonic current for torque density improvement.Compared to traditional strategies,the proposed control strategy can increase torque density of forward and reverse torque by 1.22%and 1.40%,respectively.The experimental results verify the analysis and simulation results,as well as prove the effectiveness of the proposed strategy.

Numerical simulation of the flow field of a flat torque converter

A flexible flat torque converter was proposed to fulfill the requirement of miniaturization and power density maximization for automobiles.Constructed by two arcs joined by lines,the torus was designed directly from design path.The influence of flatness on the performance of the torque converter was evaluated.The software CFX and standard k-ε model were adopted to simulate the internal flow fields of the torque converter under different flatness ratios.The results indicated that the performance of the torque converter got worse as the flatness declined,but the capacity of pump increased.The efficiency and the torque ratio dropped slightly as the flatness ratio decreased.So the torque converter could be squashed appropriately to get high power density without too much efficiency sacrifice.But when the flatness ratio was below 0.2,there was a significant drop in the efficiency.

Design of a Novel Dual Flux Modulation Machine with Consequent-Pole Spoke-Array Permanent Magnets in Both Stator and Rotor

In this paper,a novel dual flux modulation(DFM)machine with consequent-pole spoke-array permanent magnets(PMs)in both stator and rotor is proposed to achieve a larger torque density than regular flux modulation machines.The stator has two portions of PMs,one is set next to the stator slot with circumferential magnetization,and the other is inserted between the stator yoke and flux bridge with radial magnetization.The rotor has consequent-pole spoke-array PMs and alternative flux bridges.The proposed DFMPM machine can be regarded as the combination of the flux switching PM(FSPM)machine and vernier PM(VPM)machine.First,the structure and operational principle are introduced.Then,the proposed 12-stator-slot/10-rotor-tooth dual flux modulation permanent magnet(DFMPM)machine is compared with the FSPM machine and VPM machine in terms of flux lines distribution,back-electromotive force(EMF),cogging torque and average torque.Finally,the four proposed DFMPM machines are optimized for maximum average torque and minimum ripple torque considering the effects of split ratio,slot opening ratio,PM depth,PM angle and iron angle.

A Novel Axial Flux Stator and Rotor Dual Permanent Magnet Machine

A novel structure of axial flux stator and rotor dual PMs Vernier machine is presented as an effective option for high torque-density direct-driven applications.The key is to locate PMs on both sides of rotor and stator.With dual PMs,this proposed machine with a novel structure generates an improved torque per armature current at low speed.It is very suitable for direct drive applications with limited space such as the in-wheel electric vehicle(EV)motors.The theory of the structure with PMs on both sides is analyzed theoretically.The structure and operation principle of machine are introduced and the steady and steady performance of machine is analyzed and verified with time-stepping finite element method(TS-FEM).

Development of a New Flux Switching Transverse Flux Machine with the Ability of Linear Motion

This paper proposes a new rotary flux switching transverse flux machine with the ability of linear motion(FSTFMaLM),in which both the stator and the rotor cores are made by using soft magnetic composite(SMC)materials.With the special design pattern,for the rotary motion model,the proposed machine can combine both the advantages of the flux switching permanent magnet machine(FSPMM)and the transverse flux machine(TFM).It can output with relatively high torque density,and as there is no windings or the magnets on the rotor cores,the proposed machine can operate in the high speed region to improve the output power.With the adoption of the SMC materials,the manufacturing of this machine can be quite easy.By stacking the rotor core together and prolong it with the determined length in the axial direction,in addition with the special control algorithm,the proposed machine can have the ability of the linear motion.In this paper,the operation principle of this machine has been explained and the design methods are also presented.To seek the better performance,the main dimension of the machine is optimized,and for the performance evaluation,the finite element method(FEM)is adopted.The proposed machine can be used for the electric driving systems,robotic systems or other applications where the linear motion ability is required.

Fast Design Method of Variable Flux Reluctance Machines

In this paper,a fast design method is developed based on a combination of analytical and finite element(FE)methods for variable flux reluctance machines(VFRMs).Firstly,the feasibility of using analytical method in optimization under unsaturated condition is confirmed.Then,by applying the FE method,the influence of magnetic saturation is considered.Compared with the unsaturated case,the optimal split ratio for magnetically saturated case is increased by 1~1.2 times,the optimal rotor pole arc ratio varies within 0.33~0.44,and the stator pole arc ratio remains the same.Based on this,the optimal structural parameters can be initially set by analytical method and then refined by the FE method.Due to the fast speed of analytical method,less variable counts and narrowed variation ranges,the proposed method is significantly faster than the conventional pure FE based global optimization.Finally,the proposed method is used for optimizing the 6-stator-slots VFRMs having different numbers of rotor poles.The 6-stator-slot/7-rotor-pole(6s/7r)VFRM is found to have the highest torque density.It is prototyped and tested to verify the analyses.

A Novel Stator and Rotor Dual PM Flux Modulated Machine

A novel structure of Veriner permanent magnet(VPM)machine is presented as an effective option for high torque density direct-driven applications.The key is to locate PMs on both sides of rotor and stator,and design the stator PMs as a cylinder shape,the rotation of which can be controlled by an external driven system.With this design,magnetic field in the airgap can be directly regulated by the rotation of stator PMs.The structure and operation principle are introduced and the performance is analyzed with time-stepping finite element method(FEM).Analysis results show that the novel structure has really high torque density and good field weakening performance.