Efficient and Economically Optimized Way to Limit Inrush Current in an Induction Motor Using Solid-State Devices

Abstract

The paper proposes the development of a solid-state-based soft starter. It is a device that protects the motor from sudden influxes of power by limiting the large inrush of current during startup by gradually ramping up the voltage to rated, hence, producing the gradual start. It is used in an application that requires speed and torque control only during startup. Compared to conventional DOL direct online starters in which inrush current is five to ten times the rated current, the paper presents the development and implementation of a technique that provides precise control over inrush current. The added feature of a smooth stop provides protection against hammering in submersible motors. It not only satisfies the existing needs but also takes up less space than variable frequency drive (VFD); hence, stand out distinctively from the rest of its type thus making itself quite marketable. To make the solution economically viable and less complex, a fully analog-based circuit has been presented which significantly reduces the cost compared to microcontroller-based circuits.