Patent ID: 6081092
Filing Date: 2000-06-27
Classification: H02P

Abstract:
A driver circuit for a synchronous, alternating-current motor comprising a stator with at least one winding arranged around a substantially U- or C-shaped pack of magnetic plates between pole ends of which a permanent-magnet rotor (4) is mounted for rotating, the driver circuit (10) comprising:a first triac connected in series with the winding between a terminal of an alternating-current voltage supply, the first triac having a gate connected to an intermediate point of the stator winding of the motor;a second triac connected between the intermediate point of the winding of the motor and the terminal of the voltage supply to which the first triac is connected, anda control circuit connected to the gate of the second triac, the control circuit operable to, each time the motor is connected to the voltage supply:initially make the second triac conductive and consequently cut off the first triac for a predetermined initial period of time, andcut off the second triac and allow the first triac to become conductive after the predetermined initial period of time,so that, during the predetermined initial period of time, only a portion of the winding of the motor is connected to the voltage supply by via the second triac and, after the predetermined initial period of time, the whole winding of the motor is connected to the voltage supply.