DESIGN AND CONSTRUCTION OF A POWER ELECTRONIC CONVERTER FOR HIGH-POWER APPLICATIONS: AC-AC CONVERTER MOTOR STARTER

Direct Online starter for electric motors have been found to exhibit various challenges, which include high power consumption during startup, low efficiency, harmonic distortion, and high operational cost. This study presents the design, construction and performance evaluation of a three-phase AC-AC power converter-based motor starter to address most of these challenges. It incorporates digital control, monitoring and protection features for efficient industrial motor operation and energy management. This was achieved using an Arduino microcontroller, TRIAC-based firing circuit, voltage and current sensors, thermal and humidity sensors, and an LCD interface to display operation parameters in real time. The designed and developed AC-AC converter was tested using a three-phase inductor motor with a capacity less than the rated capacity of the converter (8KW). The results of the performance when using the AC-AC converter were compared with the conventional Direct-On-Line (DOL) starter and the Proteus simulation model. The experimental results revealed that the AC-AC converter effectively minimised inrush current and power demand both at startup by 3.5A and during continuous operation by 765.42W compared to the DOL system. Steady-state analysis indicated a 34.6% energy saving, attributed to improved phase-controlled voltage regulation. Furthermore, the system maintained a steady voltage output with minimal drop between 3V and 4V per phase. Overall, the study demonstrated improved soft-starting, monitoring, protection, and extended motor lifespan, confirming suitability for industrial applications.