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Würzburg, Germany

Wang K.,University of Sheffield | Zhu Z.Q.,University of Sheffield | Ombach G.,Brose Fahreugteile GmbH and Co
IEEE Transactions on Energy Conversion | Year: 2014

This paper presents feasible slot/pole number combinations of machines with two slot-pitches. They are becoming popular since they not only exhibit the low torque ripple but also the low harmonic content of the magnetomotive force. Some examples of such windings are reported in the literature, but they are limited to a specific slot/pole combination. On the contrary, a general theory is presented in this paper. The main rules for the design of such windings are illustrated and the relationship of slot (N8 and pole (2p) number, and winding topologies for machines with two slot-pitches is derived. Then, the average torque, torque ripple, eddy current magnet loss, and saliency ratio of machines with slot/pole combinations N8 = 2(2p ± 1) and N 8 = 2(2p ± 2) are investigated by the finite-element method and compared with the conventional one. The N8= 2(2p ± 1) machines have the high average torque and the low-torque ripple compared with N8 = 2(2p ± 2)machines. In addition, the eddy current magnet losses for both machines are limited, and the saliency ratio of the interior permanent magnet (IPM) machine is improved compared with the conventional slot/pole number combinations. Finally, the experimental results on surface-mounted permanent magnet and IPM machines are given for validation of theoretical analyses and finite element (FE) results. © 2014 IEEE. Source


Wang K.,University of Sheffield | Zhu Z.Q.,University of Sheffield | Ombach G.,Brose Fahreugteile GmbH and Co | Koch M.,Brose Fahreugteile GmbH and Co | And 2 more authors.
Proceedings of the 2013 IEEE International Electric Machines and Drives Conference, IEMDC 2013 | Year: 2013

This paper investigates the torque characteristics of an 18-slot/10-pole fractional-slot surface-mounted permanent-magnet (SPM) machine and presents its comparison with conventional 9-slot/10-pole and 12-slot/10-pole SPM machines by analytical and two-dimensional (2-D) finite element analysis (FEA). The winding factors of the 18-slot/10-pole machine are firstly analyzed, and then, its back-EMF, average torque, cogging torque, and torque ripple are investigated. In addition, the influence of magnetic saturation due to stator current excitation on the average torque and torque ripple is also studied by 2-D FEA. The results show that the torque ripple can be suppressed while the average torque can be improved in the 18-slot/10-pole SPM machine compared with the 12-slot/10-pole SPM machine, while the unbalanced magnetic force in the 9-slot/10-pole SPM machine can be eliminated. Finally, the experimental results are given for validation of theoretical analyses and FE results. © 2013 IEEE. Source


Wang K.,University of Sheffield | Zhu Z.Q.,University of Sheffield | Ombach G.,Brose Fahreugteile GmbH and Co | Koch M.,Brose Fahreugteile GmbH and Co | And 2 more authors.
COMPEL - The International Journal for Computation and Mathematics in Electrical and Electronic Engineering | Year: 2015

Purpose - The purpose of this paper is to investigate the influence of stator and rotor pole number combinations together with the flux-barrier layers number on the performance of synchronous reluctance machine with emphasis on output torque capability and torque ripple. Design/methodology/approach - AC synchronous reluctance machine (SynRM) or permanent magnet assisted SynRM presently receives a great deal of interest, since there is less or even no rare-earth permanent magnet in the rotor. Most of SynRM machines employ a stator that is originally designed for a standard squirrel cage induction motor for a similar output rating and application, or the SynRM machine with 24-slot, four-pole are often directly chosen for investigation in most of the available literature. Therefore, it is necessary to investigate the influence of stator and rotor pole number combinations together with the flux-barrier layers number on the performance of SynRM machine with emphasis on output torque capability and torque ripple. Findings - The average torque decreases with the increase of the pole numbers but remain almost constant when employing different stator slot numbers but with the same pole number. In addition, the torque ripple decreases significantly with the increase of the stator slot number. The machine with double-layer flux-barrier in the rotor has the biggest average torque, while the machines with three- and four-layer flux-barrier in the rotor have almost the same average torque but their value is slightly smaller than that of machine with double-layer flux-barrier. However, the machine with three-layer flux-barrier has the lowest torque ripple but the highest torque ripple exists in the machine with double-layer flux-barrier. Research limitations/implications - The purely sinusoidal currents are applied in this analysis and the effects of harmonics in the current on torque ripple are not considered in this application. Originality/value - This paper has analyzed the torque ripple and average torque of SynRMs with considering slot/pole number combinations together with the flux-barrier number. © Emerald Group Publishing Limited. Source

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