Design Analysis and Implementation of A 0.5 KVA Uninterruptible Power Stabilizer

Abstract

This paper presents design analysis and implementation of a 0.5 KVA uninterruptible electronic power stabilizer (UPSz). Poor and instability of power supply delivery in Nigeria necessitated the need for a device that can stabilize voltage, protect equipment from damages and also provide power to the loads in the absences of electricity from the utility mains. This need motivated the design of a power stabilizer (UPSz). Method of Pulse with modulation (PWM) was adopted. This method is capable of modulating a varying input to a stabilized output. Two input sources were considered; a fluctuating 220 V volt mains supply and a constant 12 V battery. The 12 V battery was rectified to provide an AC power supply to the load in the absence of the utility mains. The control circuit ensured a stabilized output voltage from input range of 140 V to 260 V AC power supply which is about ±40V to the usual supply voltage from the utility mains of 180V-220V in Nigeria. Appropriate protection circuits were incorporated against surges to which ensured the safety of home/office appliances. A variac was used to obtain various AC voltage levels during the testing. The voltage and current results at different loadings (in watts) of the UPSz were obtained. These results were compared with those of commercially readily available offline UPS of the same rating. The UPSz unlike the commercially available types delivered a stabilized voltage of 220 V to different loads of 60 W to 400 W range at a fluctuating input voltage range of 140 V to 260 V. This showed that the designed UPSz is an improved and better device than the offline equivalent. Other advantages include portability (light weight) and less expensive (relatively cheap).