Yuichi Yoshikawa

Recent technical trends in variable flux motors

This paper reviews recent technical trends in variable flux motors. Permanent magnet motor is a major component to realize high torque density with keeping high efficiency. However, when high speed revolution is required for further miniaturization, as well as the large torque in the low speed region, the flux yielded by the permanent magnet encounters a serious trade-off, i.e. the former needs less flux and the latter requires much. The solution for this trade-off is varying the flux. In general, the flux of the permanent magnet is constant, and many efforts are under development to overcome this as to be shown in this paper.

Design of Ultra Low acoustic Noise and High Power Density Direct Drive Machines with Double Rotor and Toroidally Wound Structure

According to downsizing the motion applications, high torque and power density are the most serious requirements for electric machines. Double rotor and toroidally winding permanent magnet motor is proposed to solve the problem and it is suitable for direct drive system. But it has a large cogging torque that generates the large acoustic noise. In this paper, we design the direct drive IPM motor and discuss the design method of double rotor and toroidally winding permanent magnet motor for improving the acoustic noise. We show the stator design to minimizing the cogging torque and IPMSM rotor design for sinusoidal back-EMF waveform. We discuss the FEA results and the experimental results of prototype motor. We designed 1.25kW, 50Nm prototype motor. In our experiments, the prototype motor achieved 50% higher power density and 5dB improvement of acoustic noise compared with the conventional type

Study of permanent magnet motor using a three-dimensional bend core

In this paper, to provide a reduction in size and weight of the motor, improvements to the torque density by the use of a three-dimensional bend core motor was examined. The motor using the three-dimension bend core can collect the flux leakage. The torque density was able to be improved by 20% by effectively using the magnetic flux. As a result, the reduction in size and weight of the motor becomes possible, and the performance gain of the automobile or robot can be expected.