Detection of rotor asymmetries of induction machines in an encoderless control scheme

Different techniques for the asymmetries in the rotor of asynchronous machines in closed-loop controlled drives have been developed; they usually need to monitor currents and speed. This paper investigates the detection of rotor asymmetries in field oriented controlled induction machines based only on the measured currents and without the measurement of the speed. The paper uses the indicator for asymmetries in the rotor of induction machines that was proposed in an earlier paper and extends it to the case of sensorless control schemes. The main focus of the paper is not in the sensorless control at low speed and supposes therefore that a simple model based on the voltage equation of the machine is sufficient. The region of low operation frequencies represents therefore no problem for the detection procedure. Laboratory measurements corroborate developed algorithm.