Soft Starter of Single Phase Pump Motor

In single-phase induction motor of ratings beyond a certain limit of withstand take very large currents and low powe factor while being started directly from a 1-phase supply. In order to mitigate the adverse effects of starting torque transients and high inrush currents in induction motors, a popular method is to use electronically controlled soft-starting voltages utilizing TRIAC. Normally soft-starters are used for avoiding this problem and to achieve smooth starting of large capacity induction motors. Soft starters use ac voltage controllers to start the induction motor and to adjust its speed. The performance of a voltage controlled large induction motor soft starter has been improved, resulting in nearly perfect current and torque profiles. Soft starters are used as induction motor controllers in compressors, blowers, fans, pumps, mixers, crushers and grinders, and many other applications. Starting torque pulsations are eliminated by triggering back-to-back-connected TRIAC at proper points on the first supply voltage cycle. The soft starter is connected in motor drive during the starting condition only and once the motor get its rated speed then the soft starter is disconnected from the main motor system so that the motor get protected.