Title: Improved torque in PM brushless motors with minimum difference in slot number and pole number

Authors: Mohd Saufi Ahmad; Nurul Anwar Abd Manap; Maher Faeq; Dahaman Ishak

Addresses: School of Electrical and Electronic Engineering, Universiti Sains Malaysia, 14300 Nibong Tebal, Penang, Malaysia. ' School of Electrical and Electronic Engineering, Universiti Sains Malaysia, 14300 Nibong Tebal, Penang, Malaysia. ' School of Electrical and Electronic Engineering, Universiti Sains Malaysia, 14300 Nibong Tebal, Penang, Malaysia. ' School of Electrical and Electronic Engineering, Universiti Sains Malaysia, 14300 Nibong Tebal, Penang, Malaysia

Abstract: This paper presents design, modelling and prototyping of three-phase permanent-magnet brushless machines having a fractional slot to pole ratio. In particular, permanent magnet brushless machines which exhibits slot number and pole number differ by either ±2 or ±1 will be considered. Such small difference in slot and pole numbers will potentially improve motor characteristics and subsequently result in better motor performance. Having fractional slot-pole number motors may also facilitate the deployment of double-layer windings or single-layer windings in order to simplify the manufacturing process. Finite-element methods are first used to predict the flux-linkage, back-emf and cogging torque waveforms, and they are shown to be in good agreement with the measured results. Two prototypes are built, the first motor has 12-slot/10-pole and the other motor has 9-slot/10-pole for test and validations. It is observed that the unity difference in 9-slot/10-pole motor would produce more trapezoidal phase back-emf waveform, hence, slightly higher average torque output with smaller torque ripples, in comparison with that found in 12-slot/10-pole motor.

Keywords: back-emf; brushless machines; flux linkage; finite element method; FEM; cogging torque waveforms; permanent magnet motors; PM brushless motors; slot number; pole number; modelling.

DOI: 10.1504/IJPEC.2012.048046

International Journal of Power and Energy Conversion, 2012 Vol.3 No.3/4, pp.206 - 219

Received: 16 Aug 2010
Accepted: 25 May 2011
Published online: 07 Aug 2014 *

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