Sewing machine control device with an inverter for controlling an induction motor

摘要

A sewing machine control device performs a closed loop control of an induction motor without using an encoder for detecting the motor speed. The control device includes an inverter for driving the induction motor, and controls the inverter output so that the actual speed of the motor is brought into coincidence with a target speed instructed from a speed instruction device. When the control device executes the inverter control, it uses not only the target speed fed from the speed instruction device but also a detection signal generated from a needle position detector that represents the position of a needle bar and the moving speed thereof.