The main circuit of the soft starter control panel is typically composed of three pairs of anti‑parallel thyristors in the three‑phase circuit, connected in series with the motor stator circuit. By adjusting the thyristor’s firing delay angle (i.e., the conduction angle), the system controls how long the voltage conducts in each AC half‑cycle, thereby continuously adjusting the output voltage. This allows the motor to start from a lower voltage and gradually increase voltage, rather than starting at full voltage all at once.
During the starting process, the controller monitors the motor’s operating status in real time, typically by sampling the current signal, and some systems also estimate the motor speed based on operating conditions. The system compares this real‑time data with an internally preset starting curve (such as a voltage ramp curve or current limit curve). Once a deviation between the actual operation and the set target is detected, the controller automatically adjusts the firing angle of the thyristors, and the output voltage changes accordingly.
This dynamic adjustment is a closed‑loop control system. The soft starter control panel ensures that the motor starts smoothly according to preset parameters, reducing starting current and mechanical stress, and improving the stability and reliability of the entire system.
