Speed and position sensorless permanent magnet synchronous motor drives

Abstract

DC motors have played a crucial rule in drive technology during the last few decades of this century. Recent developments in power converters, digital signal processors and magnetic materials make it possible to use ac motors in a variety of drive applications. Permanent magnet synchronous (PMS) motors are gaining wide recognition over other types of motors in drive systems, mainly due to their inherently advantageous features. For successful operation of PMS motor drives, position and speed sensing are of critical importance. Conventional sensors are expensive and hamper sturdiness of industrial drives. Hence speed and position sensorless PMS drive draws wide attention. In this work, an algorithm is developed which enables the PMS drive to operate successfully at any speed (from zero to twice the rated value) without any mechanical speed and position sensors while keeping the maximum out put voltage of the inverter constant above the base speed. New expressions have been derived for the rotor speed and position in terms of the stator voltages and currents. A method has also been suggested to calculate the input voltage of the motor. The present work is an attempt to provide theoretical analysis of speed and position sensorless PMS drives with computer simulations of various drive configurations. Experimental results which are in agreement with the proposed algorithm have been included.