Fractional-slot concentrated-winding (FSCW) synchronous permanent magnet (PM) machines have been gaining interest over the last few years. This is mainly due to the several advantages that this type of windings provides. These include high-power density, high efficiency, short end turns, high slot fill factor particularly when coupled with segmented stator structures, low cogging torque, flux-weakening capability, and fault tolerance. This paper is going to provide a thorough analysis of FSCW synchronous PM machines in terms of opportunities and challenges. This paper will cover the theory and design of FSCW synchronous PM machines, achieving high-power density, flux-weakening capability, comparison of single- versus double-layer windings, fault-tolerance rotor losses, parasitic effects, comparison of interior versus surface PM machines, and various types of machines. This paper will also provide a summary of the commercial applications that involve FSCW synchronous PM machines.

Fractional-Slot Concentrated-Windings Synchronous Permanent Magnet Machines: Opportunities and Challenges

A nonlinear adaptive lumped parameter magnetic circuit model is developed to predict the electromagnetic performance of a flux-switching permanent-magnet machine. It enables the air-gap field distribution, the back-electromotive force (back-EMF) waveform, the winding inductances, and the electromagnetic torque to be calculated. Results from the model are compared with finite-element predictions and validated experimentally. The influence of end effects is also investigated, and optimal design parameters, such as the rotor pole width, the stator tooth width, and the ratio of the inner to outer diameter of the stator, are discussed.

Analysis of electromagnetic performance of flux-switching permanent-magnet Machines by nonlinear adaptive lumped parameter magnetic circuit model

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

A three-phase, segmental-rotor, flux-switching synchronous motor is presented for the first time, with both field and armature windings placed on the stator. Mutual coupling of the circuits is through segments whose motion causes switching of flux in the armature circuit. The magnetic geometry is substantially different to that of other flux-switching machines (FSMs), and may offer advantages in terms of torque density and controllability. This paper describes the principles and the evaluation of a three-phase design, based on a 12-tooth stator with an eight-segment rotor, before introducing a prototype machine and test results. The prototype has been found to have torque density and profile comparable to that of a switched reluctance motor (SRM) of the same size.

A Wound-Field Three-Phase Flux-Switching Synchronous Motor With All Excitation Sources on the Stator

This paper presents a new class of brushless motor as an alternative to the permanent magnet brushed motor used in the automotive industry. The new flux switching motor is a very simple motor to manufacture and coupled with a power electronic controller requiring only two power semiconductor switches it has the potential to be extremely low cost in high volume applications. The design of the motor and its simulation using coupled circuit and time-stepping finite element analysis is presented. Tested performance has matched well with design targets and with simulation and is delivering performance comparable to a permanent magnet brushed motor. The new motor and drive are very robust, requiring only two power MOSFETs and a simple micro-controller to create an extremely low cost variable speed drive for automotive applications.

Flux switching motors for automotive applications

This paper presents the results of a new flux switching motor and drive offering high power density and an extremely low cost power electronic controller. The motor contains a DC field winding and a bifilar armature winding, both on the stator with a simple and rugged salient pole reluctance rotor. The power electronic controller requires only two ground referenced power transistors. This delivers electronic commutation, high dynamic performance, speed and torque control at an extremely low cost. The design of the motor and its electronic controller is described and test results of a complete drive delivering 2 kW at 15000 r/min are presented.

B.V. Gorti

Papers

Low cost, high power density, flux switching machines and drives for power tools