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.

Overview of Stator-Permanent Magnet Brushless Machines

This paper reviews the current technologies used in high-speed electrical machines through an extensive survey of different topologies developed and built in the industry and academia for several applications. Developments in materials and components, including electrical steels and copper alloys, are discussed, and their impact on the machines' operating physical boundaries is investigated. The main application areas pulling the development of high-speed machines are also reviewed to better understand the typical performance requirements.

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High-Speed Electrical Machines: Technologies, Trends, and Developments

This paper overviews the recent development and new topologies of flux-switching (FS) machines, with particularly emphasis on the permanent magnet (PM) type. Specific design issues, including winding configurations, combinations of stator and rotor pole numbers, rotor pole width, split ratio, etc., are investigated, while the torque capability of selected FSPM machines is also compared.

Advanced Flux-Switching Permanent Magnet Brushless Machines

The multilevel method has been presented for design optimization of electrical machines and drive systems for optimal system performances and efficiency in our previous work. For framework design of the multilevel optimization method, four techniques are presented in this paper, including the sizing equation, local sensitivity analysis, global sensitivity analysis, and design of experiments techniques. For each technique, a general and theoretical analysis procedure is presented before the application study. To demonstrate the effectiveness, a permanent magnet claw-pole motor with soft magnetic composite core and 3-D finite-element analysis model is investigated to minimize the material cost and maximize the output power while keeping the volume constant. The calculated motor performance based on this 3-D finite-element model has been verified by the experimental results. As shown, these techniques are simple to implement, and the resultant multilevel optimization framework can significantly improve the motor performance and reduce the required sample number of finite-element analysis.

Techniques for Multilevel Design Optimization of Permanent Magnet Motors

This paper overviews various switched flux permanent magnet machines and their design and performance features, with particular emphasis on machine topologies with reduced magnet usage or without using magnet, as well as with variable flux capability. In addition, this paper also describes their relationships with doubly-salient permanent magnet machines and flux reversal permanent magnet machines.

Switched flux permanent magnet machines — Innovation continues

This paper proposes a novel permanent-magnet (PM) flux switching (PMFS) machine with an outer-rotor configuration for in-wheel light traction applications. The geometric topology of the outer-rotor PMFS machine is introduced, and the analytical sizing equations are derived to determine the main design parameters of the machine. Two-dimensional finite-element analysis (FEA) models are developed to investigate and optimize the machine performance. Furthermore, the flux-weakening capability of the machine is analyzed and further improved by segmental PMs with iron bridges. The machine performance predictions by 2-D FEA models are validated by experimental tests on the prototype machine. The suitability of the proposed outer-rotor PMFS machine for in-wheel light traction application is demonstrated.

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A Novel Permanent-Magnet Flux Switching Machine With an Outer-Rotor Configuration for In-Wheel Light Traction Applications

The permanent magnet (PM) flux-switching linear motor, which is developed from the PM flux-switching rotary machine, possesses similar advantages such as high power density and simple structure. Furthermore, the PM flux-switching linear motor has a potential for mass production at low cost, since the expensive coils and magnets are both set on the short mover. However, the detent force which is induced by both slot-effect and end-effect deteriorates the motor performance. Some methods to reduce detent force which are effective in PM linear synchronous motors do not work in PM flux-switching linear motors, due to their special structure. This paper describes a new method to reduce the detent force by fixing assistant teeth on the mover ends. Finite element analysis shows some interesting results which will be detailed in this paper.

A New Method for Reduction of Detent Force in Permanent Magnet Flux-Switching Linear Motors

We propose a new topology for a permanent-magnet flux-switching (PMFS) linear machine. We describe its unique structure and compare it with the conventional PMFS linear machine. Finite-element analysis (FEA) shows that the proposed machine not only inherits advantages from the conventional PMFS machines, but also possesses many new merits such as more efficient usage of magnets, high fault tolerance, and easy assembly. These positive features make the proposed machine suitable for many applications. We prototyped both the conventional and proposed machines for verification and found good agreement between FEA and the experimental results.

A Modular Permanent-Magnet Flux-Switching Linear Machine With Fault-Tolerant Capability

Permanent-magnet flux-switching (PMFS) machine offers high torque density, impressive flux-weakening capability and mechanical ruggedness because of its distinctive configuration, and is potentially suitable for the application in automotive integrated-starter-generators (ISGs). However, the PMFS machine generally exhibits higher cogging torque compared with other machines commonly used in ISGs. Minimisation of the cogging torque in the PMFS machine for its utility in ISGs is therefore of particular importance. Four rotor topologies are proposed here as cost-effective means to suppress the cogging torque of a PMFS ISG. The validity of the proposed techniques has been confirmed by both two-dimensional finite-element analysis and experimental results. Moreover, the influence on the back electromagnetic force by these techniques is also investigated.

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Cogging torque suppression in a permanentmagnet flux-switching integrated-starter-generator

Cogging torque in permanent magnet flux-switching machines (PMFSM) is relatively high compared with other types of PM motors, because of their unique doubly salient structure. In this study, a new rotor teeth axial pairing (RTAP) technique is proposed. As verified with both 2-D and 3-D finite element analysis, as well as laboratory tests, the RTAP technique can effectively reduce the cogging torque, while its implementation is more flexible than the conventional rotor teeth circumferential pairing (RTCP) technique. Furthermore, the RTAP technique is also applicable to other types of machine with a salient iron rotor.

Meng-Jia Jin

Papers

A Novel Permanent-Magnet Flux Switching Machine With an Outer-Rotor Configuration for In-Wheel Light Traction Applications

A New Method for Reduction of Detent Force in Permanent Magnet Flux-Switching Linear Motors

A Modular Permanent-Magnet Flux-Switching Linear Machine With Fault-Tolerant Capability

Cogging torque suppression in a permanentmagnet flux-switching integrated-starter-generator

Cogging torque reduction in permanent magnet flux-switching machines by rotor teeth axial pairing