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This paper assesses the post-demagnetization performance of interior permanent magnet (IPM) ac machines by employing the more accurate recoil line approach based on a 2-D transient finite-element analysis (FEA). The method predicts continuous demagnetization of each magnet element undergoing partial demagnetization and evaluates the machine behavior after an event of short-circuit faults across its terminals. Along with the short-circuit faults, a failure in a drive controller or a position sensor, which may lead to a reverse voltage across the machine terminals that can eventually be more fatal and can cause significant reduction in the performance due to high levels of demagnetization, is analyzed as the worst case scenario. The FE predicted post-demagnetization performance is validated by experimental measurements in which a six-phase IPM machine designed for electric vehicle traction is allowed to lose its synchronization with the inverter when forced to operate on a torque–speed envelope, which is way beyond the drive voltage setting. [ABSTRACT FROM AUTHOR]

This paper proposes a generic approach to reduction of magnetomotive force (MMF) harmonics in permanent-magnet machines with multiple three-phase concentrated windings. Analytical equations for the MMF distributions of the proposed multiple three-phase concentrated windings are derived, and the principle for harmonic cancellation is established and validated by finite-element analysis. A new 18-slot 14-pole nine-phase winding machine in which all sub-MMF harmonics are eliminated is presented based on the proposed generic approach. The proposed approach is also applicable to other slot–pole combinations with concentrated windings except for slot number being equal to 1.5 times the pole number. Retaining all the advantages of the concentrated windings, the new technique improves the fundamental winding factor, enhances the fault tolerance capability, and reduces the detrimental effects of lower and higher order MMF harmonics on the machine, such as high rotor eddy-current and iron losses, less reluctance torque, acoustic noise, and vibration. [ABSTRACT FROM AUTHOR]

This paper discusses the development of new winding configuration for six-phase permanent-magnet (PM) machines with 18 slots and 8 poles, which eliminates and/or reduces undesirable space harmonics in the stator magnetomotive force. The proposed configuration improves power/torque density and efficiency with a reduction in eddy-current losses in the rotor permanent magnets and copper losses in end windings. To improve drive train availability for applications in electric vehicles (EVs), this paper proposes the design of a six-phase PM machine as two independent three-phase windings. A number of possible phase shifts between two sets of three-phase windings due to their slot–pole combination and winding configuration are investigated, and the optimum phase shift is selected by analyzing the harmonic distributions and their effect on machine performance, including the rotor eddy-current losses. The machine design is optimized for a given set of specifications for EVs, under electrical, thermal and volumetric constraints, and demonstrated by the experimental measurements on a prototype machine. [ABSTRACT FROM AUTHOR]

The paper is concerned with new winding configurations and associated pole-slot combinations for permanent magnet (PM) machines that lead to improved performance and facilitate cost reduction. Compared to the current state of the art, the salient feature of the proposed designs is elimination and/or reduction of undesirable space harmonics which result from the existing fractional-slot per phase per pole permanent magnet machines with concentric windings. This will bring the benefits of significant reduction of the eddy current loss in the rotor permanent magnets, short end-winding and hence reduced copper loss and copper usage, increased power/torque density, reduction in manufacturing cost, and improved energy efficiency. Although the proposed technique is primarily aimed for brushless permanent magnet machines, it is also applicable to synchronous reluctance machines, induction machines and synchronous wound field machines. The proposed technique is applied to the design of an interior mounted permanent magnet machine for electric vehicle traction applications, and demonstrated by the measurements on a prototype machine. [ABSTRACT FROM PUBLISHER]