Static frequency converter with PWM self - Control inverter for an induction motor

This paper presents a static frequency converter that controls an induction motor according to the principle V/f = constant. Unlike the classic V/f control scheme, the proposed method insures high dynamic performances from the adjustable speed drive system. The solution is based on a certain behaviour of the PWM self-control inverter in a transient state, which feeds the induction motor, thus simplifying the control circuit. By choosing a control program of controllable semiconductor IGBT or GTO devices within a PWM - SC inverter, high dynamic performances can be obtained for the asynchronous machine fed by such an inverter, due to the additional voltages that appear at the inverter output. These voltages determine a fast damping of the machine transient currents and allow reaching rapidly a corresponding value of the excitation current i0 for the new steady-state.