Transducerless position and velocity estimation in induction and salient AC machines

This paper presents a viable transducerless rotor position and velocity estimation scheme for PWM inverter driven induction, synchronous, and reluctance machines with the capability of providing robust and accurate dynamic estimation independent of operating point, including zero and very high speeds, light and heavy loading. The injection of a balanced 3 phase high frequency signal (500 to 2 kHz) generated by the inverter, followed by appropriate signal demodulation and processing combined with a closed-loop observer, enable the tracking of rotor magnetic saliencies from the machine terminals. Although rotor magnetic saliency is inherent within reluctance machines, and most synchronous machines, saliency in the induction machine is introduced via a modulation of the rotor slot leakage with minimal detrimental effects on the machine performance. Experimental verification for the induction machine is included