A new speed observer for an induction motor using the speed estimation technique

A new speed observing algorithm for vector controlled induction motor, especially suitable for low speed operation, is proposed. A pulse generator generates pulse trains of which frequency is proportional to the motor speed. However, at low speed, the time interval between pulses becomes too long to detect the actual speed between the pulses. A new speed observer to solve this problem is fundamentally composed by combining the conventional speed calculator and speed sensorless speed estimator. Although the estimated speed signal involves an error caused by parameter mismatching, it is accurate enough to be interpolated between two pulses. The fundamental algorithm and experimental results of the proposed new speed observer is shown in this paper