The soft-starter is an electronic device made of thyristored bridges, SCRs in the anti-parallel configuration activated by an electronic board, Gates A69 to control the starting current of three-phase AC motors. Its application is common in centrifugal pumps, fans, and motors of high power whose application does not require the variation of speed. The soft-starter controls the voltage across the motor through the power circuit, consisting of six SCRs, varying the firing angle thereof and consequently varying the effective voltage applied to the motor. Thus, we can control the starting current of the motor, providing a “soft start” (English soft start), so as not to generate sudden electrical voltage drops in the mains, as in direct starters.

These devices work with the technology called by-pass, which, after the motor starts and receives all the voltage of the network, a contactor is turned on and replaces the thyristor modules, avoiding their overheating. Soft-starter is applied in Centrifugal Pumps, Alternatives (Sanitation / Irrigation / Oil), Fans, Extractors, Blowers, Air Compressors, Refrigeration (Screw / Piston), Mixers, Aerators, Centrifuges, Crushers, Grinders, Wood Menders, Refiners Rotating Furnaces, Saws and Planers (Wood), Mills (Balls / Hammers), Freight Conveyors.