Direct torque control and current limitation method in start up of an induction machine

The latest development in AC motor control to emerge is direct torque control (DTC). Mainly, DTC decreases the parameter sensibility problems characterizing the field oriented control of induction machines and increases torque dynamic performance as against a PWM inverter supply. On the other hand, under start up, a high torque dynamic can cause important current transients and destroy the switch powers of the inverter. After a theoretical description of DTC principles and transient current problems in start up, the authors present a control method to limit the stator current amplitude. Simulation results are carried out and analyze with a 7.5 kW induction machine.