Permanent magnet (PM) brushless machines having magnets and windings in stator (the so-called stator-PM machines) have attracted more and more attention in the past decade due to its definite advantages of robust structure, high power density, high efficiency, etc. In this paper, an overview of the stator-PM machine is presented, with particular emphasis on concepts, operation principles, machine topologies, electromagnetic performance, and control strategies. Both brushless ac and dc operation modes are described. The key features of the machines, including the merits and drawbacks of the machines, are summarized. Moreover, the latest development of the machines is also discussed.

This paper proposes a novel wireless power transfer (WPT) system with switch-controlled capacitor (SCC) where variable capacitance and efficiency optimization are realized. The optimum asymmetrical voltage cancellation (OAVC) control is applied to realize wide-ranging soft-switching operation for the active bridge converters. The pulse width of the active bridge inverter regulates the output voltage, and the pulse width of the active bridge rectifier optimizes power delivery efficiency. The SCCs in the transmitter and the receiver side are regulated for the zero-voltage switching (ZVS) operation and the resonant condition, respectively. The online estimation of mutual inductance is carried out to adapt the coupling deviations of the WPT system in real time. A 650 W prototype is built to verify the feasibility of the proposed WPT system and the effectiveness of the OAVC control. The experiment results show quite good performance and efficiency improvement for the WPT system at various loads.

In recent years, a three-level T-type inverter has attracted considerable attention due to its advantages, such as simple structure and higher efficiency. However, the reliability of a three-level T-type inverter is particularly important as increased power switches are used. Therefore, a fault-tolerant three-level T-type inverter is proposed in this paper. Fault diagnosis and fault-tolerant control strategies for power switches both in half-bridge and neutral-point bridge are investigated. Under fault-tolerant operation, redundant fourth-leg is used to balance neutral-point voltage and the low-frequency voltage oscillation is eliminated completely. The fault ride-through capability and high-quality output waveforms can be obtained. The effectiveness of the proposed inverter topology and control methods is validated by the simulation and experimental results.

Open-phase fault in permanent magnet synchronous motor (PMSM) drive system occurs as the phase winding is disconnected or one leg of the inverter bridge fails. It may generate large electromagnetic torque ripple and serious mechanical vibration. Therefore, a rapid fault detection method is greatly required to identify this fault at early stage and prevent damage to the system. This paper develops a method of the open-phase fault detection and discrimination for the PMSM drive system based on the zero-sequence voltage components, in which the discrimination of the fault types, namely internal stator winding failure and switches failure of the inverter is realized. Then, appropriate fault-tolerant measures may be taken according to the different fault types. The experimental platform is established, and the experimental results verify the effectiveness of the proposed method, showing that not only the open-phase fault can be rapidly detected, but also the fault type can be effectively discriminated.

The stator-mounted permanent-magnet (SMPM) machines have some advantages compared with its counterparts, such as simple rotor, short winding terminals, and good thermal dissipation conditions for magnets. In this paper, a general power equation for three types of SMPM machine is introduced first, and then, power equations considering the specific topologies are derived. Based on these power equations, theoretical comparisons are carried out between various types of the SMPM machines. In all, eight topologies have been presented and benchmarked. It reveals that the flux switching permanent-magnet (PM) machine owns higher power density than the flux reversal PM machine and the doubly salient PM machine under same outer diameter. The comparison based on the power equation has established a foundation for optimizing the SMPM machines.

Interturn short-circuit fault is a kind of initial failure of the permanent magnet synchronous motor (PMSM) and serious consequences may be caused if it is left undetected. In this letter, a simple fault indicator is defined as the sum of the absolute values of amplitude differences between the stator currents, where the amplitudes of fundamental components of the stator currents are calculated by the frequency-tracking algorithm. Then, an online interturn short-circuit fault detection method is proposed for the PMSM. The experimental results validate the effectiveness of the proposed method.