Sensorless induction motor drive: An innovative component for advanced motion control

This paper reports the basic concept and recent industrial applications of a sensorless vector-controlled speed-control system for an inverter-fed induction motor in Japan. The vector control artificially gives the linear torque controllability, which is inherent for a separately excited DC motor, to the induction motor drive. First, in this paper, the fundamental concept of vector control is introduced. Next, representative speed-sensorless vector-control systems will be related. Also, a method for the automatic measurement of the electrical parameters of the induction motor is introduced. To know the motor parameters precisely is especially important for a speed-sensorless vector-control system. Finally, several examples of industrial applications of the sensorless speed control are described.