Determination of operating conditions of submersible induction motors from their terminal quantities

A simple scalar control method for an inverter-fed induction motor is described. The method uses the necessary speed information deduced from the motor terminal quantities to maintain constant slip operation. A simple technique is developed for estimation of the motor´s speed from its terminal voltage and current, which eliminates the requirement of speed sensing from the motor shaft by direct coupled devices. It is also found that the semiclosed-loop operation for maintaining constant slip at variable frequency by the proposed method results in less overshoot and oscillation associated with sudden load changes.<>