Transient behavior of three-phase induction motors under different starting methods using simulations

Abstract

Induction motors are key components in industrial settings, yet their transient behavior during startups specifically current spikes often drastically reduces their service life. This study evaluates a 3 HP motor using MATLAB/Simulink to compare the transient responses of direct-on-line, star-delta, and soft starting methods. Data indicates that direct-on-line starting drives the current to a critical peak, causing a sudden, harsh impact on both the motor windings and the shaft. While star-delta starting reduces current by supplying a lower voltage in the star configuration, the transition from star to delta generates a momentary current spike as the motor is subjected to full line voltage. In contrast, the soft starter proved to be the most favorable option by managing the transient phase linearly; it controls the startup through a gradual increase in energy rather than applying full voltage instantaneously. The results confirm that soft starting offers the most advantageous performance, as the incremental voltage supply dampens the starting current spike, ensuring a stable transition to steady-state operation.