DEVICE FOR DETERMINING A POSITION OF A ROTOR OF A POLYPHASE ELECTRIC MOTOR

A device for determining a rotor position in a polyphase electric motor having a first phase, a second phase and a third phase. A power control unit applies a first voltage on the first phase, and a second voltage on the second phase, the first voltage and the second voltage being periodic signals of opposite polarity, alternating between a first part and a second part of the alternating period, such as square waves. A sample unit samples a third voltage on the third phase for acquiring a first sample at a first instant in the first part and a second sample at a second instant in the second part, and a difference value between the first sample and the second sample. The difference value represents a mutual inductance between the stator coils due to the rotor position. A determination unit determines the rotor position based on the difference value.