DESIGN AND IMPLEMENTATION OF A THREE- PHASE AUTOMATIC TRANSFER SWITCH

ABSTRACT This project focuses on the design and construction of a Three-Phase Automatic Transfer Switch (ATS) aimed at ensuring uninterrupted power supply by seamlessly switching between a primary power source and an alternative (such as inverter or generator). The motivation behind this work arises from the persistent electricity challenges in Nigeria, including frequent outages and instability in power delivery, particularly affecting domestic users. The developed system monitors real-time voltage levels across three AC sources using ZMPT101B voltage sensors, and automatically identifies the most stable phase above a set threshold of 200V. The Arduino Nano Microcontroller behaves as the core control logic, which processes sensor input and triggers the appropriate relay to power the load. Supporting modules include a 16x2 I2C LCD for live voltage display, and an HC-05 Bluetooth module that enables remote monitoring via a mobile device. Power is supplied through a 7.4V battery stepped down by a buck converter to 5V. The system is lightweight, portable, and built using components such as three 3.3V relay modules, LEDs, a push-button switch, and a PCB Matrix Board. Test results confirmed the system’s ability to maintain voltage stability, minimize switching delays and ensure autonomous operation with minimal human intervention. Challenges, including inadequate power supply from a 2A rated buck converter leading to partial component failure, were documented and addressed with recommendations for future improvement. The project demonstrates how low-cost, microcontroller based ATS systems can enhance electrical reliability in small-scale or residential applications.