Comparative study of motor high inrush current mitigation by improvisation of soft starter firing angle using PSCAD

Abstract

Inrush current can be determined as current drawn by an induction motor during start-up period. This starting current will shoot up about 5 to 7 times of rated current. Usually, it was occurred at the starting period of induction motor and effect the lifetime of motor.To overcome this, several techniques can be implemented to reduce the high starting current. One of the technique isusing the soft starter which is the most convincing because of its simplicity in configuration, easy to control and low cost. The configuration involves power semiconductor devicewhich is thyristor that acts as a switch to control the current flow from power source to the motor. The current output can be controlled by varying the firing angle. Thechanging of firing angle is managed by a firing angle control circuit. The whole research was conducted through PSCAD/EMTDC software. In simulation, the power source, AC voltage was connected directly to the induction motor called direct on-line (DOL) and the DOL circuit was simulated to analyse the inrush current. From the simulation of DOL, the soft starter was added to the original circuit. The firing angle for soft starter was changed to several angles and what can be concluded that the high current succeed to mitigate with the altering firing angles.Simulation DOL and soft starter method were carried out with 3 different rated power which were 116kVA, 232kVA and 435kVA. Higher rated power resulting higher inrush current. As for the overall result, the inrush current was mitigated for all 3 rated power by using soft starter with the best adjusted firing angle.