Determination of soft starter firing angle perfomance to mitigate motor high inrush current using PSCAD

Inrush current in the simplest form can also be determine as current drawn by an induction motor during startup period. This starting current will shoot up about 5 to 7 times the rated current. However, this high current usually occur in the starting period only. To overcome this, several types can be implement to reduce the high current. Nevertheless, throughout this types of starter, there are some lack on each starter. After all, soft starter are the most convincing because the simple in configuration, easy to control and low cost. The configuration just involving some power semiconductor device act as switches that control the current flow from power source to the motor. The switches is in form of thyristor and was connected back-to-hack because the system conduct in AC system. The current output can be controlled by varying the firing angle. This changing of firing angle will be manage by a firing angle control circuit. The whole research was conducted through PSCAD/EMTDC software. Firstly power source was directly connected to the induction motor and the result was simulate to analyze the inrush current. The inrush current will highly fluctuate and this result will be the reference for further simulation. Then the soft starter was add to the original circuit. This soft starter was connected in between power source and motor. The thyristor that built in soft starter act like a gate to control the voltage applied to the motor. The firing angle for current limitation soft starter was change to several angle and what can be conclude that the high current succeed to mitigate with increasing the frring angle. The current drawn for this type of starter is steadily constant. The lower current during starting took longer time for motor to reach its rated speed. This type of starter successfully reduce inrush current about 42 percent. The research then conduct the time voltage ramp soft starter. This starter use the exact same circuit from the previous soft starter but the firing angle is not fixed anymore. The angle is changing from high to low. The main idea is to increase the conduction angle which also increase the voltage applies to the motor. The voltage applied from lowest value and slowly increasing. This also mean that the current gradually been increase throughout the circuit. This type of starter manage to reduce inrush for 33 percent. Finally what can be conclude is that the soft starter was proven to mitigate inrush current. Type of soft starter that going to implement is depending on the application of motor. When the application need to control the torque is more suitable to use current limitation soft starter because the current is steadily control. On the other hand when the application on motor needed the torque to increase gradually, then the time voltage ramp soft starter is the perfect choice.