Development of an Automatic Voltage Regulator for Single-Phase Residential Loads in Ibadan, Oyo State

This project develops an automatic voltage regulator designed to protect single-phase residential electrical appliances from the damaging effects of supply voltage fluctuations in Ibadan, Oyo State, South West Nigeria. Voltage instability on the national grid, characterised by frequent under-voltage and over-voltage conditions, causes premature failure of household equipment including refrigerators, televisions, and air conditioners, resulting in significant financial losses for residents. The regulator employs a servo-motor-driven autotransformer topology controlled by a microcontroller-based sensing and switching circuit. The microcontroller continuously monitors the incoming supply voltage through a precision voltage divider and instructs the servo motor to adjust the tap position to maintain a stable 220V output within a tolerance of plus or minus 5 percent. Protection features include over-current shutdown, thermal overload detection, and an output contactor that disconnects the load during extreme input voltage conditions outside the operable range. A laboratory prototype was constructed and tested across an input voltage range of 140V to 260V, achieving a steady-state output regulation of plus or minus 3.2 percent. Response time from voltage disturbance to correction was measured at under 1.5 seconds. The design is compact, mountable on a standard domestic distribution board, and incorporates visual status indicators for user awareness. Field testing in two residential properties in Ibadan confirmed satisfactory performance under real supply conditions. The project recommends commercialisation through collaboration with local electronics manufacturers. Keywords: automatic voltage regulator, voltage stabiliser, microcontroller, power quality, Ibadan.