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The working principle of soft starter

Jan 01, 2019

Soft Starter is a novel motor control device that integrates Soft starting, Soft stopping, light load, energy saving and multiple protection functions. It is called Soft Starter abroad. The soft starter adopts tri-phase parallel thyristor as the voltage regulator, which is connected between the power supply and the motor stator. This kind of circuit is like three - phase full - control bridge rectifier circuit. When the motor is started with a soft starter, the output voltage of the thyristor increases gradually, and the motor accelerates gradually until the thyristor is fully switched on. The motor works on the mechanical characteristics of the rated voltage to achieve smooth start, reduce the starting current and avoid starting over-current tripping. When the motor reaches the rated revolution, the soft starter will automatically replace the completed thyristor with the bypass contactor at the end of the starting process to provide the rated voltage for the normal operation of the motor, so as to reduce the heat loss of the thyristor, extend the service life of the soft starter, improve its working efficiency, and make the power grid avoid harmonic pollution. Soft starter also provides soft stop function. In the process of soft stop, contrary to soft start, the voltage is gradually reduced and the revolution is gradually reduced to zero to avoid torque impact caused by free stop.

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