Exciter Design and Characteristic Analysis of a Written-pole motor

Abstract

A WPM was developed in the mid-1990s for the purpose to replace a high-power induction motor (IM) with a new high-efficiency motor [1]. Fig. 1(a) shows the structure and circuit of WPM. The interesting feature of WPM is that the magnet is demagnetized in start-up by stator’s field, unlike a general PM motor. In start-up, therefore, the WPM is free from braking torque by magnet, which is very attractive. Then just before synchronization, normally at 80% of synchronous speed, the magnet is re-magnetized by the exciter pole in Fig. 1(a). After magnetization, the WPM operates as a synchronous motor, giving high efficiency same to a PM synchronous motor. By virtue of the interesting operation, it is recorded that the efficiency of high power WPM is at least 6% higher than that of an IM. However a low-power WPM has not developed due to the specialty of its applications [1]. In this study, therefore, a 0.2hp 1-phase WPM for home appliance is newly dealt with. Particularly, this study aims to design the exciter which is most important in WPM operation.