Sensorless variable speed single-phase induction motor drive system

It is usual find single-phase induction motor (SPIM) in several house, office, shopping, farm, and industry applications, which are become each time more sophisticated and requiring variable speed drives. Considering the low cost of this machine, the adoption of sensorless speed control is the more reasonable option for SPIM drives. This paper presents a proposal for sensorless variable speed SPIM drive based on direct rotor field orientation techniques. An observer based on two independent linear close-loop control systems provides the estimation of the rotor flux and speed from the measurements of the stator currents and voltages. These estimatives are used by close-loop systems for speed control and flux regulation in order to determine the voltages to be applied in the main and auxiliary windings by a three-legs VSI inverter. None variable transformation is used in this proposal in order to eliminate the asymmetry of the stator windings of the SPIM. The performance of the proposed sensorless speed control is satisfactorily demonstrated from computer simulations considering two situations: variations on rotor speed reference and the application of mechanical load.