This paper investigates effects of a step skew structure in an interior permanent magnet synchronous motor (IPMSM) to improve the output power in the field weakening control area. In this paper, effects of the step skew during the field weakening control are evaluated by three-dimensional finite element analysis (3D-FEA) as a basic investigation. On the other hand, 3D-FEA is required to reveal characteristics of skew structures, but it is time-consuming. Therefore, we constructed a design procedure for reducing development term until a suitable skew structure is obtained although 3D-FEA is performed. Additionally, the final model developed based on the constructed design procedure can achieve a large reduction in both total harmonic distortion (THD) and torque ripple under the field weakening control compared to the typical step skew models. Furthermore, it is found that the final model can suppress the voltage and has a possibility to improve the output power, especially in the field weakening control area.

This paper described the characteristics of a hybrid field motor (HEM) with a field winding on the rotor. The proposed HEM can greatly change the field magnetic flux by the field winding, and it is possible to utilize the reluctance torque and improve the power factor. In addition, the efficiency is higher than that of the conventional hybrid vehicle drive motor in wide operating area of low torque, high torque area at low speed, and constant power area. In this paper, changes in characteristics due to changes in the amount of magnets in the proposed HEM were confirmed by several electromagnetic field analyses. As a result, it was shown that the proposed HEM can reduce the efficiency in the low-speed medium-torque range, which is rarely used in electric vehicles, and significantly improve the efficiency in the low-torque range used in regular operation.

Magnetic levitation pumps can feed liquid cleanly without mechanical contact by magnetically suspending the rotor shaft integrated with the impeller. However, surfaces of the rotor and the stator need to be protected by resin bulkheads, and then the magnetic gap length is larger than generally electrical machine. Therefore, it is difficult to generate large suspension force for 1-axis active control type magnetic levitation pumps that passively stabilize the rotor in the radial direction with repulsive force of permanent magnets (PMs). This paper proposes a new structure of the repulsion PM which can generate high suspension force even wide gap length. Five structures of the repulsion PM are investigated, and the structure that is optimized for a 1-axis active control type is analyzed with 3-dimentional finite element method (3D-FEM).

In recent years, permanent magnet synchronous motors (PMSMs) are used for many applications because of their high output density and high efficiency. On the other hand, PMSMs having low aspect ratio like flat disk are desired depending on applications. In general, PMSMs employ radial gap structure which has the air gap in radial direction. However, in flat shape, radial gap motors have relatively low torque because their effective surface area of permanent magnet (PM) is small and their coil ends occupy most of the motor volume. Therefore, in flat shape, axial gap structure which has the air gap in axial direction is frequently employed instead of radial gap motors. Since axial gap motors don't have the coil ends in axial direction, they can reduce axial length. Meanwhile, conventional axial gap motors frequently employ double stator structure. Hence, in flatter shape like `ultra-flat shape', conventional axial gap motors are not suitable because stator back yoke and PM become extremely thin. Instead of those, an axial gap motor employing C-type SMC core is proposed in this paper. Advantages of the proposed axial gap motor using C-type core in ultra-flat shape is illustrated, and then, the proposed motor is analyzed by three-dimensional finite element analysis (3D-FEA).