This paper evaluates the design of a new segmented interior permanent magnet (SIPM) machine with very wide constant power operation range. The machine uses segmentation of the rotor magnets with the help of iron bridges between magnet segments. This provides for an inherent flux-weakening capability to the interior permanent magnet (IPM) machine. A very wide flux-weakening range has been achieved by using a standard distributed stator winding only. The flux-weakening capability of the proposed SIPM motor was compared to a conventional IPM machine. The same stator was used in both machines for direct comparison. The paper also presents the design optimization process and experimental verification of the performance of the proposed machine as a case study of a 42 V alternator operation in which the speed range is from 600 to 6000 r/min.

This paper investigates inductance characteristics of a novel 14 pole/18 slot, fractional-slot concentrated-winding (FSCW) IPM machine. The variations of the self and mutual inductances were calculated analytically and also obtained from the finite element model. These results were compared with experimentally measured values of the self and mutual inductances of the prototype machine. Study of the inductance characteristics reveals that both self and mutual inductances vary with rotor positions nonsinusoidally. Presence of harmonics in the magnetomotive force (MMF) is responsible for this nonsinusoidal variation of inductances. The conventional distributed winding machine does not have these harmonics. This paper analyses the contribution of these harmonics in the Ld and Lq parameters in a dq-model of the prototype FSCW machine constructed. The self and mutual inductances were represented by a Fourier series in the inductance matrix of the machine for dq-transformation. It was seen that the difference between d- and q-axis inductance is mainly contributed by the harmonic terms of the mutual inductance.

This paper presents the design and the experimental verification of an 18-slot/14-pole fractional-slot concentrated winding interior permanent magnet machine. The prototype machine was optimized for wide constant power speed range (7:1) and very low cogging torque, two of the most important requirements for traction machines. Measured performance of the constructed prototype machine has confirmed the finite-element modeling results. Experience gained from this study has led to develop a set of design rules for the concentrated winding (CW)- interior permanent magnet (IPM) machine. Scaling up of the prototype design based on these rules is also discussed in this paper.

This paper presents a finite-element-based, multiobjective design optimization study of the fractional-slot, concentrated wound, permanent magnet synchronous machine (FSCW PMSM). Design objectives included maximization of efficiency, minimization of cost and low ripple without sacrificing torque density and wide constant power speed range. A large-scale optimization study revealed that while a V-type rotor provides high torque density, a spoke-type rotor has the benefit of low torque ripple. Quest for a design that can combine the goodness of both V- and spoke type rotors for an FSCW stator has led to a novel interior permanent magnet rotor topology referred here as Y-type. The goals of achieving maximum efficiency, minimum cost and wide CPSR were also accomplished in the proposed Y-type FSCW IPMSM. For experimental verification purpose, three fully optimized rotors - V-, spoke- and Y-type were constructed for a 12-slot/10-pole FSCW stator. Extensive experimental tests were conducted on three machines for a detailed comparison study. It will be shown that the proposed Y-type FSCW IPMSM outperforms both V and spoke-type configurations. A scaled-up version of the Y-type FSCW IPMSM shown to have satisfied many of the Freeedomcar 2020 targets, which is promising for application in electric vehicles.

Torque density of multiphase PMSMs can be enhanced by using current harmonic injection (CHI) techniques that utilize potential torque-producing nonfundamental spatial harmonics of the stator winding function (SWF) to produce an additional average torque. This possibility is ignored in the existing multiphase winding design methods that only aim at maximizing the fundamental spatial SWF harmonic, thus neglecting the remaining torque-producing spatial harmonics. These methods are also restricted by the number of machine phases. Motivated by these drawbacks in the existing methods, this paper proposes a novel heuristic algorithm for designing symmetrical multiphase concentrated windings with maximized average torque by considering all the nonfundamental torque-producing spatial SWF harmonics. The proposed approach is valid for any number of phases. Accordingly, an index is proposed to evaluate the multiphase winding performance in terms of its torque density under the CHI technique. The proposed method is formulated by using analytical treatment of the SWF, based on which, a systematic approach for calculating harmonic winding factors and evaluating the average torque is synthesized. The proposed approach is validated through case studies and experimental tests.