Evaluations on operating performances of three typical V/ f control schemes in PWM inverter drive induction motor system

The authors consider the evaluation of a PWM (pulse-width-modulated) inverter induction motor system driven by general-purpose V/f control from the point of view of operating performance. For this purpose, three basic V/f control schemes are under study. They are classified according to the control policy to be adopted as follows; (i) the ratio of stator voltage to frequency is kept constant (Type I); (ii) the magnitude of stator flux is kept constant (Type II), and (iii) the magnitude of rotor flux is kept constant (Type III). Operating performances become better in the orders Type I, II, and III. In particular, Type III gives an ideal aspect for V/f control and gives an ultimate control style to the induction motor