ON-LINE UPS is worldwide the most preferred choice, when it comes to protect any delicate electronic and electrical equipment or DATA, from power fluctuations and outages. It consists of three major components: Charger, Batteries and inverter. On line UPS is also known as double conversion UPS i.e. it takes raw utility AC power, converts it into clean DC power and further back into AC to feed the load un-interrupted & clean power. It uses battery as a standby source of power. In case of mains supply failure or fluctuations beyond some specified limits, the UPS switches over automatically onto BATTERY mode. As the utility supply restores normal, the UPS switches back to mains mode and starts recharging the batteries.