The main function of the soft-starter is to control the voltage across the motor by means of the power circuit, consisting of six SCRs, which can vary the firing angle of the motor, thus also varying the optimized voltage applied to the motor. In this way, it is possible to control the starting current of the motor, allowing a subtle start, so that it does not cause sudden electrical voltage drops in the mains, as in direct starters.
The soft-starter basically consists of an electronic device formed by thyristor-type bridges in the anti-parallel configuration, which are gradually driven by an electronic board, which is intended to control and optimize the starting current of three-phase AC motors LHB08100099. Its use is common in centrifugal pumps, fans and motors of high power, in which the application does not need the variation of speed.
This device usually operates from a technology called by-pass, which after the electric motor starts and receives all the mains voltage must be connected a contactor, which will be able to replace the thyristor modules, thus avoiding possible overheating of the same.