Investigation of winding MMF harmonic reduction methods in IPM machines equipped with FSCWs

Abstract

Summary In this paper, implementation of fractional‐slot concentrated windings (FSCWs) into an interior permanent magnet (IPM) machine, designed by using the same geometrical and operational specifications as Toyota Prius 2010 IPM machine, has been presented. In detail, the Toyota Prius's IPM equipped with integer‐slot distributed windings has been considered as a reference machine. Then the geometry of the stator has been adequately modified in other five models to equip FSCWs and adopt different magnetomotive force (MMF) reduction methods. It has been validated that the FSCW technique causes a significant increase in the rotor losses due to increase in the rate of the total harmonic distortion of the MMF harmonics. To reduce the effect of these harmonics, different MMF harmonic reduction methods including phase‐winding coils with different number of turns, multilayer winding with phase shifting, and stator with flux barriers have been investigated. To reveal the effectiveness of the investigated MMF harmonic reduction methods, the key thermal and electromagnetic performance characteristics including torque, torque ripple, power losses, and efficiency have been numerically calculated by finite element method and have eventually been compared.

Comparative study on performance characteristics of PM and reluctance machines equipped with overlapping, semi‐overlapping, and non‐overlapping windings

“…It has also been revealed that for small power applications, it might me be more reasonable to use FSCW topology because of the moderate output power with high efficiency. However, as shown in [2,3] for large power application, since a large amount of the cooling equipment might be required because of the large eddy current induced in the rotor part. In addition, excessive eddy currents can further lead to a high rotor temperature particularly at high speeds, and hence the rotor magnets will suffer from a high risk of irreversible demagnetisation [29,30,45,46].…”

“…Therefore, reduction of copper loss can be achieved by optimising the design for maximum efficiency (very limited improvement), implying various magnetomotive force (MMF) reduction methods, such as flux-barriers, different number of turns per phase, phase shifting etc. [2] or introducing a new winding topology having very short-end windings with very low MMF harmonic content. In [3], a new winding topology, called novel semi-overlapped winding (NSW), has been introduced by presenting the influence of winding parameters on the performance characteristics and merits/demerits of the proposed winding by comparing the electromagnetic performance characteristics of the interior permanent-magnet machines (IPMs) having different winding topologies.…”

“…an extensive research on reduction of MMF harmonics has been conducted. In [2], several different MMF harmonic reduction methods have been implemented into an IPM with FSCW and very limited improvement has been achieved. It has been shown that the FSCW topology is not suitable for the IPMs used in large power applications, and particularly variable speed applications.…”

Design and analysis of interior permanent magnet machines equipped with novel semi‐overlapping windings

“…The aim of reducing the end‐winding axial length is to decrease the most dominant machine loss, which typically is the stator copper loss, and to decrease the total axial length to reduce the space requirement (promote compactness) of the electrical machines. The most recent performance improvement methods related to electrical machine windings have been listed as follows. Multi‐layer fractional‐slot concentrated windings (FSCWs) and integer slot concentric windings with phase‐shifted and un‐even number of turns per coil side [7–19, 38–41]. In addition, FSCWs having more than two layers [9, 11, 16–19, 29–31, 33, 39].…”

Magnet shifting for back EMF improvement and torque ripple reduction of a TORUS‐type nonslotted axial flux permanent magnet machine

“…AFPM machine is one of the best candidates for use in many applications such as renewable energy applications, electromechanical traction drives, electric cars, and marine propulsion system. Regarding the number of stator and rotor discs, AFPM machines are classified into three categories: single‐sided structure, double‐sided structure, and multi‐stage structure . The double‐sided type is the most widely used type of AFPM motor .…”