Soft starter uses three opposite-parallel thyristors as voltage regulators. With such a circuit, such as a three-phase full-controlled bridge rectifier circuit, when the motor is started by a soft starter, the output voltage of the thyristor is gradually increased, and the motor is gradually accelerated until the thyristor is fully guided. Through, the motor works on the mechanical characteristics of the rated voltage to achieve a smooth start, reduce the starting current, avoid starting the overcurrent trip, and connect it between the power supply and the motor stator.
The voltage is slowly increased from zero to the rated voltage, so that the starting current of the motor during the starting process is controlled by the uncontrollable overload current in the past. And the starting current can be adjusted as needed. There is no impact torque in the whole process of starting the motor, but a smooth start-up operation. This is the soft start.
Soft starters generally have the following starting methods:
(1) ramp boost soft start;
(2) ramp constant current soft start;
(3) step start;
(4) Pulse shock start;
