Control device for synchronous-alternating voltage electric motor, has controlling unit releasing connection with voltage source in proximity of zero-crossing based on magnetic polarity and rotational direction during starting of motor

摘要

The device has a signaling device (3) supplying an electrical signal indicating a polarity of an input voltage and zero-crossing. A magnetic field sensor (4) supplies another electrical signal representing a magnetic polarity of a rotor. A processing and controlling unit (5) is connected with activation and signaling devices and with the sensor. The controlling unit releases the connection with a voltage source to a moment in the proximity of zero-crossing of the voltage based on the magnetic polarity and the rotational direction desired for a motor (M) during starting of the motor.