Optimized AC-AC Converter Design Using Triode Technology For Voltage Regulation And Soft-Starting Applications In Three-Phase Induction Motors

Abstract

Induction motors are extensively utilized in industrial applications due to their robustness, energy efficiency, and minimal maintenance requirements. However, the high inrush current during startup presents significant challenges, particularly for the durability of electrical components and overall system stability. This study proposes an optimized AC-AC converter using the phase angle control method with TRIAC for voltage regulation, enabling gradual voltage adjustment during the startup process. To enhance system reliability and mitigate electrical interference, an optoisolator circuit is integrated into the design. The developed AC-AC converter demonstrates effective voltage control, capable of adjusting the phase angle within the range of 0° to 180°. This enables the soft-starting of a three-phase induction motor, significantly reducing inrush current spikes. Experimental results show that the soft-starting method reduces the initial current of a 0.5 HP three-phase induction motor under no-load conditions to 0.72 A, compared to 1.54 A during direct-on-line (DOL) starting. Furthermore, when loaded, the starting current increases slightly, accompanied by a temporary decrease in motor rotational speed. These findings highlight the potential of AC-AC converters as an economical and efficient solution for soft-starting in industrial motor applications.