부산대학교 도서관

Energy saving in electric motors is important for variable-speed drives. Permanent magnet (PM) motors exhibit high power and efficiency. The operation of PM motors can be controlled by magnetic flux weakening to decrease the back-EMF at high speed because the magnetic flux in the PM is constant. However, the flux-weakening control technique at high speed may cause significant iron and copper losses and high harmonic iron losses. In this paper, a variable-magnetization technique for the PM by a field due to small magnetizing current is proposed to achieve variable back-EMF. Thus, a novel PM motor capable of varying the magnetization of the PM is proposed. Our results indicate that the proposed PM motor is capable of varying the magnetization on the load and achieves compatibility between a wide variable back-EMF range and a small magnetizing current.