Comparative Analysis of Direct and Soft Starting Method for Induction Motor on Difference Load Levels

Abstract

Asynchronous machines are considered nowadays the most commonly used electrical machines, which are mainly used as electrical induction motors. The induction motors, which is considered as the backbone of industrial applications and operation, demand a reliable and efficient starting method to minimize mechanical stress and electrical disturbances. This research study presents a comparative analysis of Direct Online (DOL) and Soft Starter techniques for three-phase induction motors, utilizing MATLAB/Simulink software for simulation and performance evaluation. The simulation results highlight the effectiveness of the soft starter in achieving a faster and more controlled start-up, making it a superior choice in applications where reducing start-up transients and mechanical wear is critical such as conveyors, pumps and compressors. This was achieved by deploying a 35-kW induction motor to analyze the performance of direct online (DOL) starters and soft starters, with a particular focus on the latter's use of a thyristor block to mitigate inrush current. The analysis was carried out at different load conditions, such as no load, 25% load, 50% load, 75% load, and 100% load. The result obtained shows that, the direct online takes longer transient than the soft starter, for example, during no load test direct online transient time was 0.4 second while soft starter was 0.2 second. This study underscores the significance of advanced simulation tools in optimizing motor startup strategies, thereby enhancing the efficiency and longevity of three-phase induction motors.