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The direct driven permanent magnet synchronous motors are applied in many equipments, such as wind generator, machine tool, electric vehicle, fun and so on. Among different topologies, the outer-rotor permanent magnet synchronous motor (OPMSM) has the merit of high torque density. This paper investigates a kind topology structure of OPMSM, which adopts PM surface-mounted rotor and fractional-slot structure. First, the topology of motor structure is introduced. Second, the performance of initial design is investigated. Third, the OPMSM is optimized with global PSO algorithm in order to lower the cost. The skewed PMs are adopted to further decrease the torque ripple. Finally, the OPMSM with four-piece Halbach PM array is analysed. It shows the optimized OPMSM can meet the application requirements after adopting either skewed PMs or Halbach PM array.

In an induction motor with broken rotor bars, stator currents contain fault-related components. The fault information propagates to voltages when the motor is in a closed-loop control. The control has an effect on the currents and voltages. Relying solely on the currents or voltages is difficult to obtain an accurate detection and quantification of the fault. A new online diagnosis method, which takes both currents and voltages into consideration, is proposed in this study. A fault severity factor is proposed to evaluate the extension of the fault, which is almost independent of the control parameters. Furthermore, the method can be applied to different control strategies. The effectiveness and robustness of the proposed method have been validated by experimental results.

Parameter identification plays an important role in speed estimation schemes. This paper presents a speed estimation scheme based on second-order sliding-mode supertwisting algorithm (STA) and model reference adaptive system (MRAS) estimation theory, in which both variations of stator resistance and rotor resistance are deliberately treated. A stator current observer is designed based on the STA, which is utilized to take the place of the reference voltage model of the standard MRAS algorithm. The observer is insensitive to the variation of rotor resistance and perturbation when the states arrive at the sliding mode. Derivatives of rotor flux are obtained and designed as the state of MRAS, thus eliminating the integration. Furthermore, in order to improve the near-zero speed operation, a parallel adaptive identification of stator resistance is designed relying on derivatives of rotor flux and stator current. Compared with the first-order sliding-mode speed estimator, the proposed scheme makes full use of the auxiliary sliding-mode surface, thus alleviating the chattering behavior without increasing the complexity. The robustness and effectiveness of the proposed scheme have been validated experimentally.

—This article deals with proposed solutions for five-phase induction motor drives, specifically aimed to sensorless vector control under an open-phases fault. Exploiting the modified transformation matrices for dual planes, the motor model in the synchronous frame is established under open phases. Torque ripple is reduced by particular magnitude ratio currents. Furthermore, the third harmonic current is used to improve iron utilization and torque density. The proposed sliding-mode observer method for wide-range speed estimation combined with online resistance identification is investigated, especially for low-speed operation. Experimental tests are performed to validate the effectiveness of the proposed method.

This paper proposes a new current based diagnosis method, which is the so called current product signal analysis method (CPSA), for rotor fault diagnosis in induction motors. The major theoretical principles of CPSA are presented in this paper and it is shown that rotor faults can be effectively detected. Extensive simulation and experimental results confirm the effectiveness and merits of the proposed diagnosis approach, especially when the motor is at very low slip.

This paper presents a sensorless on-line Motor Current Signature Analysis (MCSA) method to detect and locate an inter-turn short-circuited fault in the stator winding of the induction machine (IM). It is appropriate for the monitoring of Volts/Hertz controlled inverter-fed systems. The phase-shifts between adjacent line currents of both fundamental harmonic and principal slot harmonic (PSH) are analyzed. Then the fault severity and the fault location feature are derived, respectively. For the purpose of phase signal extraction, synchronous reference frame filter and adaptive phase locked loop (PLL) are integrated into the monitoring system. The robustness and effectiveness of the proposed scheme has been validated by means of laboratory tests.

This paper proposes a new method to diagnosis rotor faults in rotor field oriented controlled (RFOC) induction motors (IMs). It is theoretically proved that the ratio between the amplitude of the oscillating component and the average of torque current in the d-q reference frame allows detection and quantification of the extension of the fault. Motor parameters are not needed except for the number of rotor bars. At the same time, the reference speed and the load level do not significantly affect the diagnosis results. The effectiveness of the scheme has been validated by simulation results.

This paper proposes an improved Sliding-Mode Observer (SMO) for the sensorless control of a five-phase induction motor, which substitutes a sigmod function for the sign function. The conventional SMO is robust against parameter variations and disturbances, however, it has serious chattering problem in the steady state. The proposed method is utilized to reduce the chattering, and the rotor flux is also obtained from SMO for direct field oriented control. The convergence of the improved SMO is analyzed, and sufficient conditions are given to prove the stability. Simulation and experimental results are verified the effectiveness of the proposed method.