Patent ID: 6903532

Claim:
A starting circuit for an electric induction motor having a plurality of phase windings to be energised from an electricity supply, the phase windings having at least three terminals for connection to the supply, the circuit comprising a first switching means arranged and controllable to conduct a uni-directional current derived from the supply between a first combination of the terminals to establish a stationary rotor flux in the rotor of the motor, a second switching means arranged and controllable to supply a starting current between a second combination of the terminals selected to generate a stator flux at an angle to the stationary rotor flux, switch control means to control the first switch means to establish the stationary rotor flux and to control the second switching means to initiate supply of the starting current to provide a starting torque for the motor, and back EMF sensing means to sense a back EMF generated by rotation of the rotor to sense whether the rotor has turned sufficiently to be in a condition to connect the motor to the supply.