Abstract: A three-phase induction motor control apparatus resorting to a slip frequency control type vector control system having three-phase sine wave generating device, first operation device, second operation device, and vector operation device; whereby a current command value and a frequency command value are determined in accordance with a difference between a set velocity and a real velocity to determined a control current value. The three-phase sine wave generating device generates a three-phase sine wave having a frequency according to the frequency command value. The first operation device multiplies one of outputs, which are outputted from the three-phase sine wave generating device and mutually have a phase difference of 120.degree., and a preset value to determine one current component value.

Abstract: A standard-length positioning apparatus wherein acceleration and deceleration of a driving mechanism for actuating a mechanism for feeding a material is controlled by a digital positioning mechanism according to a position feedback. Marks marked on the material are read by a sensor during the deceleration of the driving mechanism, and the digital positioning mechanism outputs a signal for stopping the driving mechanism when it receives the read-in output of the sensor while the driving mechanism is being decelerated. When a signal from the sensor is not received by the digital positioning means while the drive is being decelerated, the digital positioning mechanism utilizes feedback pulses of a positioning detector to stop the drive.