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The reduction of cogging torque is the most important design objective for electric power steering (EPS) motors, because the rotation characteristics of the motor are directly transmitted to a driver. Therefore, a variety of optimal design methods are applied to reduce the cogging torque for EPS motors. However, the measured cogging torques of fabricated models are significantly greater than the finite‐element analysis (FEA) results, because the additional harmonic components (AHCs) of the cogging torque are generated by manufacturing tolerances. The cogging torque generated by manufacturing tolerances can be divided into two components, which are generated by stator and rotor tolerances. In this study, AHCs, which cause cogging torque, are analysed by FEA by applying various tolerances to the analysis model, and harmonic analysis is also conducted. The relation of AHC generated from the stator and rotor is analysed by a rotor swapping test. Consequently, this study can be helpful to analyse the components of the cogging torque generated by manufacturing processes. [ABSTRACT FROM AUTHOR]

In order to exhibit high performance, traction drive motors that use rare-earth magnets have been mainly applied to hybrid and electric vehicles (EVs). However, the raw materials of the magnets have critical issues such as unstable supply and high cost. Thus, a variety of motors not using rare-earth materials have been intensively developed for the traction motor. Nevertheless, it has limitation in increasing the performance of such motors without the use of rare-earth magnets. Accordingly, this paper investigates the availability of a spoke-type ferrite-magnet motor (FMM) with a novel rotor configuration for EV traction motors. In particular, the proposed motor has two rotor designs, and its characteristics based on finite-element analysis are compared according to each rotor design. Furthermore, various mechanical characteristics such as thermal stability, structural safety, and acoustic noise are checked in the design stage of the spoke-type FMM. Finally, the spoke-type FMM is tested in order to verify its performance and feasibility, including vehicle installation and on-road test in LA4 city driving mode. [ABSTRACT FROM PUBLISHER]

Rare-earth magnets have been widely employed for traction drive motors of hybrid and electric vehicles (EVs) due to high energy density. Nevertheless, the magnets have critical problems such as unstable supply and high cost. Recently, in order to solve the problems, a variety of motors not using rare-earth materials have been reviewed, such as an induction motor, a switched reluctance motor, and a spoke-type ferrite magnet motor (FMM). In this paper, a modified spoke-type FMM with a novel rotor configuration was presented for a traction motor of low-speed EVs. The characteristics of the modified spoke-type FMM are numerically compared with a conventional spoke-type FMM at the same design condition. Finally, the modified spoke-type FMM is fabricated and tested in order to verify its performance and feasibility. [ABSTRACT FROM PUBLISHER]

On account of high efficiency and high power density, permanent-magnet synchronous motors (PMSMs) are mainly applied to a high-speed machine. Especially, because of relatively easy magnetic circuit design and control, a surface-mounted PMSM of them is adopted in almost the entire high-speed applications. However, the surface-mounted PMSM has some weak points due to a sleeve, which is nonmagnetic steel used in order to maintain the mechanical integrity of a rotor assembly in high-speed rotation. The sleeve causes additional eddy current loss in the rotor besides permanent magnet and increases not only magnetic air-gap length but manufacturing costs by raw material purchase and shrink fitting. Thus, in this paper, a new rotor shape for a high-speed interior permanent-magnet synchronous motor (IPMSM) is presented in order to resolve the faults of the surface-mounted PMSM. Moreover, the amount of permanent magnet employed in the IPMSM is decreased by approximately 53% than that of the surface-mounted PMSM. Except for the rotor configuration, all design conditions of the IPMSM are identical compared with the surface-mounted PMSM. Finally, the IPMSM is fabricated, and its superiority and reliability in high-speed operation are verified by test. [ABSTRACT FROM PUBLISHER]

This paper deals with two types of interior permanent magnet (IPM) motors, S-type and V-type. The V-type is optimized in the rotor shape to obtain better performance than the S-type. In general, average operational torque (AOT) and torque ripple of IPM motors are greater than those of other permanent magnet motors due to reluctance torque. This reluctance torque is generated by permanent magnet arrangement in the rotor of IPM motor and causes noise and vibration. Therefore, this paper presents the optimal V-shape, based on the finite-element method, of permanent magnet in the V-type by robust design, called Taguchi method, to reduce torque ripple and improve the ratio between torque ripple and AOT than S-type. [ABSTRACT FROM AUTHOR]