Permanent magnet motor with reversible salient poles and variable magnetic force

To operate motors at a higher efficiency over a wider range of speeds, we have developed a technique that quickly reverses the salient poles in permanent magnet (PM) motors. With this technique, PM motors can change negative salient poles into positive salient poles by applying the magnetization of the PM. Furthermore, we discuss the combination of reversible salient poles with variable magnetic force to increase the efficiency of the motor under partial load. This paper proposes a novel PM motor that uses our proposed technique to reverse saliency and describes the principle of reversible pole saliency as well as the resulting motor characteristics. When the proposed motor operates with a negative salient pole, a higher torque is produced at low speeds; when the motor reverses to a positive salient pole, higher power and efficiency are produced at high speeds. These results confirm that the proposed motor can reverse the saliency direction of the pole and that this reversibility allows the motor to achieve high torque at low speeds and high power at high speeds. Consequently, the motor can operate over a wide range of speeds. © 2017 The Institute of Electrical Engineers of Japan.