The soft starter is a motor control device that integrates motor soft start, soft stop, light load energy saving and various protection functions. The soft starter is mainly composed of three opposite parallel thyristors connected in series between the power source and the controlled motor and its electronic control circuit. Different methods are used to control the conduction angle of the three opposite parallel thyristors, so that the input voltage of the controlled motor changes according to different requirements, and different functions can be realized. Soft starter principle: Soft starter (also known as soft starter, motor soft starter, soft starter) Soft starter adopts technical methods such as step-down, compensation or frequency conversion to achieve smooth starting of motor and mechanical load, reducing starting current to the grid. The degree of impact allows the grid and mechanical systems to be protected.