This paper investigates the open-circuit fault-tolerant current control for a five-phase fault-tolerant permanent-magnet (PM) machine used for electric vehicles. By relieving the common constraint of zero neutral point current in the existing fault-tolerant control strategies and reconfiguring the maximum round rotating magnetomotive force under different fault conditions, the new current sets, which enable the five-phase PM machine to output the maximum smooth torque, are obtained by the analytical method. Compared with the existing fault-tolerant control strategy, larger torque and lower torque ripple can be obtained with the proposed fault-tolerant control strategy, and the five-phase PM machine can safely operate with the loss of up to three phase windings. The proposed fault-tolerant control strategy is verified by both finite-element analysis and experimental results. The developed fault-tolerant current control strategy can be generalized into any multiphase PM machines.

The series-parallel hybrid electric vehicles (HEVs) are widely developed due to the advantages of high fuel economy and good driving performance. The electronic continuously variable transmission, which is a key part of the HEV, can be based on planetary gear or compound structure machine (CSM). The axial magnetic-field-modulated brushless double-rotor machine (AMFM-BDRM), which can be connected with a traditional permanent-magnet synchronous machine to form a CSM, is investigated in this paper. The axial tilting torque is analyzed, and the necessary condition for avoiding it is given. Compared with the single-sided topology, the double-sided AMFM-BDRM is recommended to eliminate the axial tilting torque. The influences of winding turns, diameter ratio, ferromagnetic block and permanent-magnet (PM) dimensions, air-gap length, phase current, and internal power-factor angle on the power factor and electromagnetic torque are analyzed, and it is found that the increase of power factor is sometimes at the expense of sacrificing the electromagnetic torque. The effects of speed and PM segmentation on losses are investigated, and the circumferentially double-segmented PM is selected. The influences of dissymmetry on air-gap flux density, no-load back electromotive force, electromagnetic torque, and axial magnetic force are analyzed, and it is found that the offset, tilt, and PM position deviation of the PM rotor have different degree effects on machine performances. Experiments are carried out, and the correctness of the analysis and simulation results are verified.

With the advantages of good driving performance and high fuel economy, the series-parallel hybrid electric vehicles (HEVs) are widely developed. Power-split device, which is a kernel part of HEV, can be based on planetary gear or compound-structure machine (CSM). The transverse-flux brushless double-rotor machine (TF-BDRM), which can form a CSM by being connected with a traditional permanent-magnet synchronous machine (PMSM), is investigated in this paper. The equivalent magnetic circuits are established, and the equivalent reluctances, and d- and q-axis armature-reaction reactance are deducted. It is found that the armature-reaction reactances are in direct proportion to pole-pair number. The reluctances of stator core, inner and outer air gaps, transverse-flux (TF) tooth and leakage reluctance are analyzed. Flux-concentration structure is investigated to increase the main flux of the machine. Flux-concentration factor EFC is used to illustrate the effect of flux-concentration structure, which can be increased by the increase of the radial and circumferential thickness of PM. The flux-density distributions of two typical situations are simulated. With manufacturing technology investigated, the TF-BDRM prototype is made, and experiments are carried out. The tested waveforms of BEMF are approximately sinusoidal, and the tested torque ripple is obvious.

The hybrid variable-flux permanent-magnet synchronous machine (VF-PMSM) is an alternative candidate for adjustable speed applications. The series magnet and parallel magnet configurations are the two existing topologies for hybrid VF-PMSMs. However, they both have drawbacks that have not been fully resolved. A premium topology with high power density and magnetization regulation using acceptable current pulses is highly desired. This paper proposes a new hybrid VF-PMSM with a quasi-series magnet configuration and a passive flux barrier. After introducing the proposed topology and its operating principles, the results of a comparative study are presented comparing the magnetization characteristics and torque capabilities of the three configurations. The influences of key design variables on the machine’s performance are investigated, showing that the proposed machine can achieve a relatively high power density comparable to the series configuration, and the required magnetization current amplitude falls within acceptable limits.

The development of traditional permanent magnet synchronous machines (PMSMs) in electric vehicle (EV) industry is limited by the unalterable permanent magnet (PM) excitation field. Variable-flux PMSMs are considered as a good candidate for EV propulsion for their ability to operate in a wide speed range with high efficiency by manipulating the magnetization state dynamically. A novel hybrid-PM variable-flux PMSM with series-parallel magnetic circuits is proposed in this paper. The structure and operating principle of the proposed machine are introduced. The electromagnetic performances of the proposed machine are analyzed and compared with the series-connected and parallel-connected variable-flux machines, and the proposed machine combines the advantages of these two kinds of machines. The inductance characteristics of the proposed machine are analyzed by frozen permeability method (FPM), and the variation laws of inductance are quite different in different magnetization states and load conditions. The torque capacity of the proposed machine is analyzed. The torque ripple can be significantly reduced and the output torque can be improved by properly applying flux-weakening control.

This paper investigates the demagnetization characteristic and permanent-magnet (PM) minimization of the less-rare-earth interior PM synchronous machines (LRE-IPMSMs) used for the electric vehicles, which are featured with high power density, high efficiency, and low cost. First, the equivalent magnet circuit (EMC) of the investigated LRE-IPMSM in demagnetization case is established. Then, the effects of the PM width and the thickness on the machine demagnetization characteristic are investigated. After that, the no-load EMC of the investigated LRE-IPMSM is established. Finally, an analytical method is proposed to obtain the minimum PM volume scheme on the premise of providing the targeted no-load flux and taking the machine anti-demagnetization ability into consideration simultaneously.