OPTIMAL SOFT STARTING OF VOLTAGE-CONTROLLER-FED IM DRIVE BASED ON VOLTAGE ACROSS THYRISTOR

-AC voltage controllers are used as induction motor starters in fan or pump drives and the crane hoist drives. This paper presents a method of identifying the end of soft start of an ac voltage-controller-fed i nduction motor (IM) drive based on the voltage across the nonconductin g thyristor through a dynamic simulation of the whole drive system. A two point current minimization technique is adopted to operate the dri ve system at the required optimal voltage under all operating conditio ns. This minimizes the motor losses. Graphic modelling of the whole dr ive system is done in a modular format using Design Star and dynamic s imulation is done using SABER. The dynamic simulation results of the w hole drive system are supported with experimental data.