Maximum-Torque and Maximum- Efficiency Rotor Flux Selection of an Induction Motor in Transient Regime

A new control strategy for Induction Motor (IM) operating at variable speed and torque is proposed in this paper. In the high speed region, the measure of rotor speed and the sensitivity to IM's parameters of the motor still remains a problem. In this context, one proposes a neural approach that ensures sensorless control and maximum torque operation. The entire purpose is to introduce a new torque maximization approach by using optimal control theory. The optimal control provides dynamic regimes with a minimum input energy. This controller design is based on a d-q IM model and allows a decoupled control of the speed and flux. Taking into account dynamic equations of the speed and rotor flux with the voltage and current boundaries constraints, the flux reference is founded to achieve the maximum torque and minimum energy at any given speed. This optimal rotor flux is implemented in a Rotor Field Oriented Control (RFOC). Aiming to check it validity, this RFOC is implemented on a 1.5 kW laboratory IM. Comparing to a conventional control law, we have obtained better performances since lowest energy consumption and the highest torque are reached in an accelerated and motoring mode.