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The low speed toothed doubly salient permanent-magnet (TDSPM) machine is an interesting candidate motor for electric ship applications because, of its high torque output, maintenance-free operation and flexible working modes, which gives the opportunity to increase system’s reliability, and decrease the system size, weight and noise which are key features for naval applications. However, particularly in the 3-phase configuration, the stator and rotor saliency of these machines leads to a high level of torque ripple. To overcome these drawbacks, the use of polyphase machines (with a number of phases greater than three) can be a relevant solution. In this paper, an optimal design of two kind of novel 4-phase motors is performed in order to fulfil the specifications of a high power naval ship propulsion. The designs aim to maximize the torque to mass ratio. The motors’ performances are directly linked to their structural parameters, so, the impact of the coil number in terms of mean torque, torque ripple, energy ratio values, and efficiency is also presented and analysed. The design of these two electromagnetic structures, as well as the determination of their electromagnetic performances, are carried out using a particle swarm optimization algorithm (PSO) with taking into account thermal constraint. The performance of the proposed machine in terms of mean torque, torque ripple, energy ratio, and efficiency values is presented and analysed. The results obtained reveal that the TDSPM machines with four poles/phase are good candidates to meet the requirements of high power direct-drive ship propulsion system.

This paper presents a results comparison synthesis of an outer and inner rotor doubly salient permanent magnet machine operating at low speed. The outer rotor design has the benefit that coils and cooling can be placed near the shaft, increasing the possible stator bore radius. Consequently, the space required for the coils inside the stator. Electromagnetic design and performances results of the machine is presented and discussed in the following paragraphs.

The subject of this article is to optimize the design and to compare the performances of a low-speed doubly salient permanent magnet machine with those of a low-speed flux-reversal machine devoted to direct drive applications. The optimization, focused on the maximization of the machines mass-to-torque ratio, is done by a genetic algorithm combined with the finite-element method (FEM). The electromagnetic characteristics of the two optimized machines, including phase flux linkage, inductances, back-electromotive forces (EMFs), and static torque, obtained from FEM analysis, are then analyzed and compared. Finally, the torque cost and the torque density of the two machines are compared with those of other topologies.

In this work, we present a torque optimization of the inset permanent magnet synchronous machine. The optimization system combines an analytical model used to calculate the air-gap flux density as well as the direct-axis and quadratic-axis inductances, with a genetic algorithm. Results of the torque optimization and the torque reported to the volume of the magnet are presented.