Patent ID: 6850863

Claim:
A method of determining the stopped angular position of a rotor in a stator of a polyphase synchronous rotary electrical machine, the stator having a plurality of windings adapted to create a magnetic field driving rotation of the rotor and each winding having one or more terminals for applying a supply voltage, which method comprises the following steps: a) applying a first sequence of successive voltage vectors to the terminals of the windings, each voltage vector defining the value of the non-zero voltage to be applied simultaneously to the supply terminals of each winding, said first sequence including first and second voltage vectors adapted to modify the electrical characteristics of the windings when the driving magnetic field created by the windings is added to the magnetic field of the rotor and a third voltage vector adapted to cancel out the torque created by applying the first and second voltage vectors, b) determining a response signal from all of the windings to application of the first voltage vector and then a response signal to application of the second voltage vector, said response signals being correlated to the angular position of the rotor, and c) establishing the angular position of the rotor with an uncertainty of ±90° from the signals determined in the step b).