STAR–DELTA STARTER

Induction motors are the primary workhorses in industrial applications, but their starting phase poses significant challenges, namely high inrush currents and abrupt mechanical torque. This project presents a comparative study of Direct-On-Line (DOL), Star-Delta (Y-Δ), and Soft Starter methods for three-phase induction motors, with a specific focus on analyzing their transient performance using simulation. To conduct this analysis, dynamic models of an induction motor and the corresponding control circuits for each starter were developed and simulated using the MATLAB/SIMULINK environment. The study evaluates key performance metrics by comparing the simulation waveforms for stator current, rotor speed, and electromagnetic torque during the startup transient. The simulation results quantitatively demonstrate the severe inrush current (up to 6-8 times full load) and high-impact torque of the DOL starter. The Star-Delta simulation illustrates its effectiveness in reducing starting current to approximately 33% of DOL, but also clearly exposes the open-transition torque dip and current spike during the switchover. In contrast, the thyristor-based Soft Starter model demonstrates superior performance, offering a smooth, stepless acceleration, precise current-limiting capabilities, and the elimination of mechanical jerk. This simulation-based analysis provides a clear, quantitative framework for evaluating the trade-offs between cost, complexity, and performance, enabling engineers to select the most appropriate starter for specific load requirements and power system constraints.