Accurate Low Speed and Torque Control for Induction Motor with Secondary Current Feedback Using MI Sensor Installed in Shaft Hole

Highly accurate speed and torque controls are strongly required for induction motors especially at a low speed to maintain an accurately constant torque through a long time operation typically for rolling spread of steel sheet production. High accuracy of the 12 feedback control system is based on a condition of clear detection of 12 waveform at relatively higher speed region over around 500 rpm where the disturbing signal for 12 coming from 11 is relatively small due to the magnetic shielding effect of the shaft steel.In this paper, tried to introduce the finite impulse response digital low-pass filter (FIR digital low-pass filter) to effectively separated of 11 and 12 waveforms showing similar low frequencies and obtained an accurate torque control result through 83 min operation case with 40 rpm speed.