Abstract-This paper deals with novel multi-phase permanent magnet machine drive to enhance drivetrain availability in electric traction applications. It describes the development of new winding configurations for 6-phase permanent magnet (PM) brushless machines with 18-slot, 8-pole, that eliminate and/or reduce undesirable space harmonics in the stator magnetomotive force (MMF). In addition to improved power/torque density and efficiency with a reduction in eddy current loss in rotor permanent magnets and copper loss in end-windings, the developed winding configuration also enhances availability of drivetrain, in a variety of applications requiring a degree of fault tolerance, by employing it as two independent 3-phase windings in a 6-phase interior permanent magnet machine (IPM), which is designed and optimized for a given set of specifications for an electric vehicle (EV), under thermal, electrical and volumetric constraints. The paper also describes the design and development of 6-phase inverter with independent control for both sets of 3-phase windings. The designs of the motor and the inverter are validated by a series of preliminary tests on the prototype machine drive.Index Terms-Electric vehicle, fractional-slot, inverter control, multiphase, permanent magnet machines, power drivetrain.
I. INTRODUCTIONERMANENT MAGNET (PM) brushless machines have been increasingly used in a variety of applications ranging from high speed manufacturing [1], electric and hybrid vehicle traction [2], ship propulsion [3], aerospace actuation [4] to wind power generation [5]. To improve torque density and efficiency, and to reduce torque ripple, a relatively newer Manuscript received December 28, 2014; revised March 19, 2015 and April 13, 2015; accepted April 16, 2015. Copyright (c) 2015 IEEE. Personal use of this material is permitted. However, permission to use this material for any other purposes must be obtained from the IEEE by sending a request to pubs-permissions@ieee.org.This work was supported in part by the European Commission for CASTOR project under European Green Vehicles Initiative (EGVI) through Grant No. 260176.V. I. Patel, and J. Wang are with the Department of Electronic and Electrical Engineering, The University of Sheffield, Sheffield, S1 3JD, United Kingdom (e-mail: v.i.patel@ieee.org, j.b.wang@sheffield.ac.uk). D. T. Nugraha, and R. Vuletić are with the Automotive System Engineering Team, Infineon Technologies AG, Munich, 85579, Germany (email: dian.nugraha@infineon.com, radovan.vuletic@infineon.com winding configuration for PM brushless machines, which is often referred to as fractional-slot concentrated or modular, has recently emerged [2], [6], [7], [8]. It offers numerous advantages over the overlapped distributed winding in conventional PM brushless machines, which include simple manufacturing due to concentrated coils of the phase around one tooth or alternate teeth [9], higher copper packing factor and lower end-winding losses resulting into high efficiency [10], and reduced probability of inter...
