Characteristics of a permanent magnet motor with reversible salient poles and variable magnetic flux

Abstract

To operate motors at higher efficiency over a wider range of speeds, we have developed a technique that quickly reverses salient poles in permanent magnet (PM) motors. In the proposed technique, the PM motors can change negative salient poles to positive salient poles by applying magnetization of PM. Furthermore, we discuss the combination of reversible salient poles with variable magnetic flux to increase the efficiency at 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 motor can reverse the saliency direction of the pole and that this reversibility allows the motor to have high torque at low speeds and high power at high speeds. Consequently, the motor can operate over a wide range of speeds.