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° but less than 180°) 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° 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° PWM drive. At the end, feasibility of a 165° drive is also discussed