Yokeless and segmented armature (YASA) axial-flux permanent-magnet machine has high power density and efficiency, which is suitable for electric traction drive, especially for in-wheel or near-wheel direct-drive electric vehicles. This paper investigates and optimizes the cogging torque of the YASA machine with soft magnetic composite (SMC) core. First, the structure of YASA with SMC core is introduced. Then, the influence of magnet pole-arc ratio, magnet skewing, stator shoe width ratio, and stator shoe shifting on cogging torque is analyzed, based on which the cogging torque is optimized by establishing the response surface model and using the genetic algorithm. Finally, the optimization results are verified by the 3-D finite-element method. The results confirm that based on a certain magnet pole-arc ratio, there exists an optimum combination of magnet skew angle, stator shoe width ratio, and stator shoe shift angle for the cogging torque minimization, while the main performances of the machine remain nearly invariable.

In the context of traction drives with required torque transient capabilities and a classically wide flux weakening speed range, this paper gives design considerations of a particular Double-Polarity (DP) five-phase machine. Beyond its intrinsic fault tolerance due its five phases, it specificity is the ability to develop torques of comparable values under three kinds of supply: with only first, third or both first and third sinusoidal currents. This property, due to first (E1) and third (E3) harmonic electromotive forces (emf) of comparable values, gives more degrees of freedom for the control of the machine. Unlike three-phase sinusoidal machine, flux weakening is no more the unique solution when maximum voltage is reached. Design considerations of such DP machines are presented: firstly, elements for the choice of slots/poles combination are given; secondly, in case of an Interior Permanent Magnet Synchronous Machine, possible adaptations of the rotor are proposed; thirdly, the level of eddy-current losses is considered, important at high frequencies. For proof of the concept effectiveness, a prototype with a five-phase fractional-slot concentrated winding of 40 slots and 16/48 poles is presented with results from experimental set-up and Finite Element modeling. A comparison with equivalent three-phase 24-slot/16-pole machine is also carried out.

A novel transverse-flux permanent magnet linear motor (TFPMLM) named as double-sided double-excited one is proposed in this paper. First, the operational principle and structural advantages of the TFPMLM are presented. Then, the 3-D magnetic circuit structure of the TFPMLM is simplified equivalently into a 2-D one in order that Schwarz-Christoffel (SC) mapping method can be adopted to analyze the motor's magnetic field and characteristics. Then, the air-gap flux density distribution, back voltage and force waveforms when at no-load and at load are calculated by the SC mapping method and 3-D finite-element method, respectively, for a prototype linear motor, The results from the two methods coincide much better with each other. At last, influences of magnet shape on the cogging force are studied by the SC method.

Using the finite-element model (FEM) to achieve the optimal design of electromagnetic devices is a complex and time-consuming process. Space-mapping techniques reduce computation cost by aligning two models with different granularities, namely, a coarse model and a fine model. In this paper, Kriging output space mapping (OSM), an original space-mapping technique based on adaptive nonlinear corrective projection, is proposed and compared with a conventional OSM technique. The device for optimal sizing is a five-phase linear induction motor, which is represented through two modeling levels: 1) coarse (Kriging model) and 2) fine (2-D FEM). An advantage of this new technique is its ability to provide a sufficiently accurate model for each objective and constraint function and make the coarse model converge effectively toward the fine model.

In this article, a novel five-phase fractional-slot concentrated winding (FSCW) with 20-slot/22-pole is presented. It benefits not only the advantages of conventional FSCW but also weak space harmonics of magnetomotive force (MMF). The winding allows eliminating the first sub-order harmonic. The new layout of the winding topology is obtained by a combination of stator shift technique of the winding in the slots with a special coupling of the windings (star-pentagon), using winding function theory. The high performances of the new winding layout are validated using the finite element method (FEM). Compared to the conventional winding, the winding factor and the total harmonic distortion (THD) of MMF are improved by 1.3% and 2.2%, respectively. With the same injection of current density, the average output torque is increased by 1% and the torque ripple is decreased by 60%. The eddy current losses in the permanent magnets (PMs) at rated speed (600 r/min) and 2100 r/min speed are improved by 67% and 56%, respectively.

A novel flux-switching transverse-flux permanent magnet tube linear motor (FSTFPMTLM) with oblique air-gap is proposed in this article, which combined the merits of the tube linear motor, the transverse-flux linear motor, and the switched-flux linear motor. The structure and operating principle of the FSTFPMTLM is presented first. Considering this motor has a 3-D magnetic circuit and designing the motor with high performance, this article proposes an optimization method for the FSTFPMTLM by decomposing the design of the motor into two steps to separate optimization using experimental design method. The first step is to optimize the cross-section part of the motor. After that the optimized motor is compared with the initial one by finite element method (FEM). The prototype is then manufactured and tested.