Protection and Controlling of Three Phase Induction Motor by Electronic Soft Starter

The project is designed to provide a soft and smooth start for 3 phase induction motor. The three phase induction motor during the initial starting condition draws much higher current than its rated capacity and the motor reaches its full speed. Due to this results in mechanical jerk and high electrical stress on the windings of the motor. Results Sometimes the windings may get burnt. The induction motor should start smoothly and it reaches the speed for safer operation. This project is designed to give a soft start to the induction motor based on the TRAIC firing triggered by heavily delayed firing angle during starting and then reducing the delay till it reaches zero voltage triggering. This results in low voltage during start and the gradually to full voltage. Thus the motor starts slowly and then slowly picks up to full speed. This project consists of a three TRAIC, two for each phase, the output of which is connected to a direct 3 phase induction motor. The charging and discharging of capacitor is interfaced to comparator results delayed in firing pulse during start and then gradually reduces the delay and motor runs at full speed. Further the project can be enhanced by using TRAIC in place of SCRs with PWM control to reduce harmonic distortions offered in various electronic devices like TRAIC triggering mechanism.