A novel sensorless control drive for an interior permanent magnet motor

In this paper, development of a novel PWM drive system for an interior permanent magnet (IPM) motor without using any current and position sensors is reported. The uniqueness of the drive system lies in defining a wide angle energisation period (more than 120/spl deg/ but less than 180/spl deg/) and modulating the voltage waveform appropriately such that the zero-cross of the induced back EMF is always detected during the current zero-cross period. Hence, the sensorless control strategy of the wide angle drive is made identical with the traditional 120/spl deg/ drive where, the turning ON of a new phase every time calls for the perfect back EMF zero-cross detection and an appropriate delay. Valid experimental results are presented for a 150/spl deg/ PWM drive. At the end, feasibility of a 165/spl deg/ drive is also discussed.