A soft starter is an electronic device used to control the acceleration of electric motors by gradually increasing the voltage supplied to the motor during startup. This controlled acceleration helps prevent jerks and mechanical shocks in the driven load. Here's how a soft starter achieves this:
Voltage Ramp-up: Unlike direct-on-line starting, where the motor receives full voltage at the moment of start, a soft starter employs a voltage ramp-up technique. It starts the motor with a lower voltage and then gradually increases it over a set period until it reaches the desired operating voltage. This gradual voltage increase results in a smoother and more controlled acceleration, reducing the likelihood of sudden jerks and mechanical shocks.
Reduced Current Surge: During direct-on-line starting, motors experience a high inrush current, which can cause mechanical stress and shocks to the driven load. A soft starter limits the inrush current by initially applying reduced voltage. This reduces the mechanical stress on the motor and the load, preventing sudden jolts and shocks.
Torque Control: Soft starters can also control the torque applied to the motor during startup. By limiting the torque, the motor accelerates more smoothly, avoiding abrupt changes in speed that could lead to mechanical shocks.
Load Balancing: Soft starters can provide phase balancing for three-phase motors, ensuring that each phase receives the required voltage and current during startup. This balanced supply helps prevent uneven torque and mechanical shocks.
Auto Bypass: Some soft starters have an auto-bypass feature that switches the motor to full voltage once it reaches a certain speed. This means that during normal operation, the soft starter is bypassed, and the motor receives full voltage, avoiding any additional voltage-related issues during steady-state operation.
By utilizing these techniques, a soft starter helps protect both the motor and the driven load from mechanical shocks and reduces wear and tear on the equipment, leading to longer equipment life and improved performance.