STEUERGERAET FUER EINEN INDUKTIONSMOTOR

摘要

A control apparatus for an induction motor and an electric car propelling motor includes an inverter for supplying a driving current to the induction motor on the basis of a predetermined control signal, a rotational speed sensor for detecting a rotational speed of the induction motor, a V/f control circuit responsive to an input speed command signal for producing a control signal for the inverter, a vector control circuit for producing an inverter control signal on the basis of the speed command signal and the rotational speed signal of the rotational speed sensor, an abnormality detecting circuit for detecting abnormality of the rotational speed sensor. A change-over circuit having inputs supplied with outputs of the V/f control circuit and the vector control circuit, respectively, selects the inverter control signal from the V/f control circuit in response to detection of abnormality of the rotational speed sensor while selecting the inverter control signal supplied from the vector control circuit so long as no abnormality is detected in the rotational speed sensor.