Patent ID: 6995539

Claim:
A device for estimating the rotor speed of at least one slip ring asynchronous machine, the asynchronous machine including a stator having a stator winding fed with three-phase voltage and current in order to generate a varying magnetic flux having a rotation speed, and a rotor having a rotor winding in which the magnetic flux generated by the stator winding induces a voltage in the rotor winding, thereby creating an electromagnetic torque which drives the rotor at a rotor speed such that the rotor speed has a slip in relation to the rotation speed of the varying magnetic flux, the device comprising: a measuring member arranged to measure the voltage in the rotor winding during at least one time period and to output a signal corresponding to the measured voltage in the rotor winding; a signal processor having a digital signal processor unit arranged to remove noise from a digital signal corresponding to the measured voltage in the rotor winding and to generate an output signal; and a calculating unit arranged to receive the output signal from the signal processor and to calculate a value of the rotor speed based on the output signal.