Flux tracking methods for direct field orientation

Numerous techniques have been reported in the literature to accomplish the task of locating the rotor flux axis for the purpose of direct field orient ation. This paper first summarizes the existing sensorless techniques using high-frequency test signal injection to determine the flux spatial locatio n in an induction machine. A novel approach employing balanced and unbalanc ed excitation is then investigated to track the flux. It is first demonstra ted that the rotating flux vector in the machine causes saturation induced saliency in the phases under normal operating conditions. By employing high -frequency test signals, this saliency is monitored and then used to track the put in the machine under test. The feasibility of the proposed approach is verified with experimental results.