Linear induction motors (LIMs) have been extensively adopted in urban railway transportation given their non-adhesion thrust and simple stator structure. However, these LIMs undergo unfavorable power factor and efficiency considering the copper and eddy losses of them. Recently, linear flux-switching permanent-magnet motors (LFSPMs) have attracted the attention of researchers due to their high power density, simple structure, easy heat dissipation, high efficiency and high power factor. However, so far, no quantitative comparison exists between LFSPMs and LIMs in the size of 1:1 to prove the feasibility for LFSPMs to be used in railway transit systems. Therefore, a comparative analysis between the two motors is also conducted. First, this study investigates the LIMs for railway transit using finite element method (FEM). Second, the LFSPMs for railway transit is designed and optimized. Third, the electromagnetic performance of the two motors are compared and analyzed through the FEM. Finally, a prototype of the LFSPMs is constructed in a small size to validate the FEM results. It is concluded that LFSPMs offer a favorable thrust force, have high efficiency, and high power factor but have large normal force and force ripple. Therefore, applying LFSPM requires reliable supporting device and shock absorber.

To incorporate the merits of simple and robust movers of induction linear motors and higher power factor and high efficiency of permanent magnet linear motors, a new long primary double-sided linear flux-switching permanent magnet (DSLFSPM) motor is proposed, investigated, and quantitatively compared with linear induction motors (LIM) for the electromagnetic launch system. First, the topology, operation principle, and electromagnetic performance of the DSLFSPM motor have been investigated. Then, in order to analyze the LIMs comprehensively, three LIMs have been designed based on the same overall dimensions and other key parameters. Finally, the electromagnetic performance of DSLFSPM motor and LIMs have been compared and summarized. The results show that the DSLFSPM motor has some merits such as higher efficiency, higher power factor, more robust mover, larger thrust force, and smaller force ripple than LIM motors. In order to validate the simulation results, a small-scale prototype of DSLFSPM motor has been built and measured.

Linear flux-switching permanent magnet (LFSPM) motors have drawn extensive concern for rail transit drive systems because permanent magnets (PM) and armature windings are all located on the short primary, whereas the long secondary is made up of iron only. Thus, the LFSPM motor with low cost and high efficiency is an excellent choice for urban rail transportation system. However, the installation of linear encoders which are expensive and unreliable along with the long stator will bring about increased costs and reduced reliability. To overcome the shortcomings and fully exert the advantages of LFSPM motors, extended Kalman filter (EKF) is adopted to achieve sensorless control of LFSPMs for its better stability, robustness and low requirements for working environment in this paper. An improving tracking performance can be obtained using EKF considering the end effects of LFSPMs and the presence of noise. Both simulation and experimental results indicate that the motor can run reliably from standstill without position sensors, which is advantageous compared with other sensorless control methods based on EMF.

In order to adapt to the single power supply system of the aircraft, this paper proposes and investigates a novel dual-winding fault-tolerant (DF) motor drive system based on the redundancy bridge arm for aerospace applications. The proposed DF motor offers the advantages of magnetic isolation, physics isolation, thermal isolation, small cogging torque ripple, inhibiting the short circuit current and high fault tolerance. The proposed DF motor drive can adapt to the single power supply system of the aircraft, reduce the drive cost, and reduce the number of independent power sources and power switches. In addition, it can improve power density, the reliability and the utilization rate of the drive. At the same time, the drive system has stronger fault-tolerant ability and it can achieve the fault tolerant control for one phase winding fault or multiphase windings fault. To realize the short-circuit fault diagnosis performance, the short-circuit fault diagnosis and processing method has been investigated. Then, to realize the fault-tolerant performance, a novel SVPWM fault-tolerant control strategy is proposed. Finally, the DF motor drive performances have been verified by experiments. The research results verify the reliability and effectiveness of the proposed DF motor drive system and SVPWM fault-tolerant control strategy.

A new double-sided linear flux-switching permanent magnet motor with a yokeless mover is proposed in this paper. First, the topology and structure of the proposed motor are presented, and the pole pitch ratio and segment number are shown to strongly affect performance. Second, the electromagnetic performance of DSLFSPM motors with a secondary yoke and without a secondary yoke are compared and described. Third, according to analytical models, air-gap flux density levels and corresponding harmonics are investigated, and force production mechanisms of the proposed motor are presented. The analytical results match to the FEA results. Finally, experiments on a prototype is carried out to validate the simulation results. Back-EMF, cogging force and inductance values of the prototypes are measured and experimental results for the drive systems are presented.

Stator wound field flux-switching (SWFFS) motors with all excitation sources placed on a stator are suitable for wind power generation systems (WPGSs) because of their simple and robust structure, nonusage of rare-earth magnets, wide speed, controllable magnetic field, and easy heat dissipation. However, the claimed advantages of SWFFS motors have not been fully investigated based on megawatt (MW)-class WPGS. Hence, an SWFFS machine is designed and investigated for semidirect drive WPGS in this paper. First, the topology and operation principle of the SWFFS machine are investigated. Second, the air-gap flux density excited by the dc field and armature currents is analyzed separately based on the Fourier analysis method. Third, electromagnetic performances, including air-gap magnetic field, flux linkage, and electromagnetic torque, are calculated by using the theoretical field model and two-dimensional finite element analysis (FEA). Fourth, the output characteristics of the SWFFS generator, such as output voltage, output power, and efficiency, under different operating conditions are obtained. Finally, the analytical model and FEA results are validated through experiments based on an MW-class prototype.