altair2017技术大会集求解器a high power factor fault tolerant vernier permanent magnet machine

1、Altair 2017 技术大会集A high power factor fault-tolerant vernier permanent-magnet machineXuhui Zhu 1,2, Wenxiang Zhao 1,2, Jian Zhu 1,2, Fangfang Bian 1,21School of Electrical and Information Engineering, Jiangsu University, Zhenjiang, 212013, China2Jiangsu Key Laboratory of Drive and Intelligent Control

2、 for Electric Vehicle, Zhenjiang 212013, China摘要： 永磁游标电机具有高转矩密度的优势，但是现在研究的永磁游标电机受限于低功率因数。为了解决这个问题，本文提出了一种高功率因数容错永磁游标电机。与传统的游标电机相比，所提出的电机具有更高的功率因数和更高的转矩密度；另外该电机还具有容错性能。通过 Altair 公司的有限元软件 Flux 对该电机的电磁性能进行了分析。： 永磁游标电机、转矩密度、功率因数、容错、FluxAbstract:Vernier permanent-magnet (VPM) machine offers the advantage

3、 of high torque density.However, the existing VPM machines usually suffer from relatively low power factor. To solve the problem, this paper proposes a new high power factor fault-tolerant VPM machine. Compared with the existing one, the proposed VPM machine has higher power factor and higher torque

4、 density. Also, the fault-tolerant capability is provided. The electromagnetic characteristics of the proposed machine are analyzed by using the finite element software Flux of Altair.Key words: Vernier permanent-magnet machine, torque density, power factor, fault-tolerant, FluxI. INTRODUCTIONDue to

5、 their high torque density, vernier permanent-magnet (VPM) machines are suitable for direct- drive applications such as electric vehicle propulsion 1 and wind power generation 2. However, they usually suffer from low power factor 3. In order to meet continued-operation requirement, a fault-tolerant

6、VPM (FTVPM) machine was proposed in 4, but its power factor is relatively low. Meanwhile, a novel VPM machine with improved power factor was proposed in 5,6, but it has poor fault tolerant capability. It is never reported that a VPM machine can incorporate the merits of high power factor and high fa

7、ult-tolerant capability.In this paper, a high power factor FTVPM machine will be proposed. It can not only retain the advantages of the conventional VPM machine, but also improve the fault-tolerant capability and power factor. In Section II, the configuration and operation principle of the proposed

8、machine will be introduced. In Section III, all the results will be analyzed by using finite element analysis (FEA) software - FLUX. Finally, thes will be drawn in Section IV.II. Configuration and operation principleFig. 1 shows the proposed 5-phase FTVPM machine as compared with the existing one 4.

9、 For the proposed FTVPM machine, its stator has 10 slots and 20 teeth. Each stator tooth is designed as multi-teeth structure by splitting it into several field modulation poles (FMPs), which serve as magnetic field modulation. Different from the existing VPM machine with distributed windings in 6,

10、the proposed FTVPM machine uses concentrated windings to reduce the copper loss and provide fault-tolerant capability. Tangential excited- 1 -Altair 2017 技术大会集PMs are uniform distributed in the inner rotor with spoke array, and the outer rotor mounts radial excitedPMs on the inner surface.FMPsFMPsSt

11、atorOuter PMsPMsInner PMsStator Outer rotorInner rotorRotorMagnetic gearstructure(a)(b)Fig. 1. FTVPM machines. (a) Existing machine. (b) Proposed machine.In the proposed machine, the modulation relationship can be expressed as:Po = ns ± Pi(1)where Po, ns and Pi are the numbers of outer rotor po

12、le pairs, FMPs and inner rotor pole pairs, respectively.Due to this particular design, the inner rotor, the outer rotor and the FMPs constitute a so-called magnetic-gear. In order to allow the motor to operate normally, the pole pair number of the windings Pw should equal to Po. Therefore, the stato

13、r and outer rotor compose a traditional PM machine. The stator, the FMPs and the inner rotor constitute a vernier machine. It is necessary for the speeds of outer rotor (Vo) andinner rotor (Vi) to meet the relationship of (2).PiVi = - PoVo(2)Due to the modulation effect of the FMPs, the magnetic fie

14、ld can be modulated into a lot of spaceharmonics in air gaps of the proposed machine. The number of PM pole pairs (Pm,k) of these harmonics can be expressed as:= iP + jnsPm,k(3)where i=1, 3, 5, j=0,±1,±2,±3, P is the number of PM pole pairs in inner rotor or outer rotor and ns is then

15、umber of FMPs.III. Performance EvaluationA. Back-EMFThe back-EMF curves produced by the outer rotor and the inner rotor are shown in Fig. 2, when the inner rotor rotates at 540 r/min and the outer rotor rotates at -1860 r/min. It should be noted that the back- EMF is lower than Ei+Eo due to the magn

16、etic saturation, where the Ei and the Eo are the magnitude of back-EMF produced by PMs on the inner and outer rotor, respectively.B. Torque characteristics- 2 -Altair 2017 技术大会集Due to the magnetic-gear structure, the no-load torque of the proposed machine is different from theconventional vernier ma

17、chine. The outer rotor no-load torque (To) and inner rotor no-load torque (Ti) should meet the relationship of (4). Since the outer rotor is at no load, its loaded torque just needs to overcomefriction and airthe loaded torques of. Thus, the loaded torque of outer rotor approximately equal to 0. Fig

18、. 3 comparesboth VPM machines at the current density of 5.7 A/mm2. All the results of loadedtorque are analyzed based on the control strategy of Id=0. The torque density of the proposed machine is40.9 kNm/m3, while that of the existing one is 30.0 kNm/m3.PT ' = PT 'o ii o(4)Fig. 2. Curves of

19、 Back-EMF.Fig. 3. Torque comparison.C. Power factorThe flux distributions of both machines are compared in Fig. 4. It is obvious that due to the designed dual-rotor structure in the proposed machine, the inner and outer rotor magnetic circuits are connected in series. Therefore, the proposed machine

20、 only has insignificant flux leakage as compared with the existing machine. As a result shown in the Fig. 5, the proposed machine has higher power factor than the existingone. Quantitatively, the power factor of the proposed machine is 0.82, while that of the existing one is 0.39.D. Fault-tolerant c

21、apabilityFault-tolerant capability ensures the machine to operate in single phase or multiple phase faults. The ratio of mutual-inductance and self-inductance of the motor is often used to evaluate the fault-tolerance performance. The mutual-inductance and self-inductance are shown in Fig. 6. The ra

22、tio equal 0.044. It issmall, thus the proposed machine has good fault-tolerant performance.IV.SIn this paper, a novel 5-phase FTVPM machine has been proposed for direct-drive application. Themachine configuration, operation principle and electromagnetic performance have been presented. Compared to t

23、he existing VPM machine, the proposed one offers the advantages of the higher torque density and higher power factor. Also, the fault-tolerant capability is obtained. Therefore, it is suitable forhigh reliability and high torque applications.- 3 -Altair 2017 技术大会集(a)(b)(c)Fig. 4. Flux linkage distri

24、butions. (a) Scale. (b) Existing machine. (c) Proposed machine.(a)(b)Fig. 5. Curves of voltage and current. (a) Existing machine. (b) Proposed machine.Fig. 6. Self-inductance and mutual-inductance.V. REFERENCES1 K Chau, C Chan, C Liu, “Overview of Permanent-Magnet Brushless Drives for Electric and Hybrid ElectricVehicles,” IEEE Trans. Ind. Electron., 2