Design of a Low-Cost Inverter System for Small-Scale Businesses in Maiduguri, Borno State

This project designs a low-cost modified sine wave inverter system intended to power small-scale business equipment during grid power outages in Maiduguri, Borno State, North East Nigeria. Frequent and prolonged power outages severely constrain business productivity in Maiduguri, compelling small enterprises including tailors, barbers, and phone repair shops to rely on expensive diesel generators. The designed inverter converts 12V DC from a battery bank to 220V AC at 50Hz using a push-pull converter topology driven by a SG3524 PWM oscillator integrated circuit. A full H-bridge output stage employing IRFZ44N MOSFETs generates the modified sine wave output. The transformer is custom-wound to achieve the required voltage step-up ratio. An output voltage feedback loop stabilises the AC output against varying battery voltage and load changes. Protection circuits address over-load, over-temperature, and low-battery conditions. The prototype delivers a continuous output power of 500VA with a measured DC-to-AC conversion efficiency of 87.4 percent under full resistive load. Total harmonic distortion was measured at 23.5 percent, which is within acceptable limits for resistive and most motor loads common in small businesses. Battery autonomy was calculated at approximately six hours for a 500Wh battery bank under a 300W average load. Component cost analysis demonstrates a 40 percent reduction compared to commercially available units of equivalent rating. Field deployment at a tailoring shop in Maiduguri confirmed operational reliability over a two-week evaluation period. Keywords: inverter design, modified sine wave, power outage, small business, Borno State.