The induction motor start up with transient suppression

The paper reports the computer simulation of transients during the induction motor (IM) start up at symmetrical and asymmetrical (unbalanced) voltage impressed. The investigation begins with clearing up the physical reason of the IM start-up transient origin and then proceeds to theoretical analysis of transient suppression methods. To suppress transient to a minimum magnitude the strategy of separate and sequential switching on the stator windings at favorable time instants to three phase mains is considered. Three possible schemes of the IM asymmetrical switching on are described, and then the mathematical modeling are carried out with help of differential equations in Cauchy form. Results of computer calculation are plotted with 3D sets of the transient currents and torques of the IM in terms of time and different phase angles of the voltage impressed.