A novel two-phase BPM drive system with high power density and low cost

A novel brushless permanent-magnet (BPM) motor drive system is proposed in this paper. The basic motor structure consists of a stator with four salient pole pieces and a six pole, permanent-magnet rotor. The proposed drive system, using four switches, fully utilizes the stator ampere-turns by providing 180 electrical degree bipolar current conduction. Hence, the use of motor materials is maximized and very high power density is achieved. In addition, the quasi-square wave back-EMF and matching current wave shape guarantee minimum peak current stress on the drive. The low stress on the power devices and efficient use of active materials result in a drive system with a lower cost than conventional three-phase BPM drives of comparable output power. The advantages of the proposed system over three-phase BPM motor drives are illustrated using sizing analysis, finite element analysis (FEA), time domain simulations and experimental studies. It can be expected that a variety of industrial applications will follow up on this new technology