UPS

Online UPS and Offline UPS are the two crucial types of UPS. Both supply power to the device in case of power outage. But the similarities end here. The main difference between Online UPS and Offline UPS is that the Online UPS provides the power with the help of rectifier and inverter combination. It simultaneously provides power to load as well as the battery so that battery can be charged to supply power in case of power failure.

On the contrary, an Offline UPS supplies AC power directly to the load by switching ON the transfer switch. And in case of power failure, the offline UPS supplies the power from the battery backup. Another crucial difference between Online UPS and Offline UPS is the requirement of the large heat sink.

Online UPS

The Online UPS consist of a rectifier, battery and inverter in-line with AC mains and load. The AC power supplied to the Online UPS is fed first to the rectifier circuit, then it will convert it into DC power. Then, this DC power is used to charge the battery, and this DC power is supplied to the inverter circuit, and then it is supplied to load. There is transfer switch, but that will always be in ON position. Thus, at every instant of time, the power delivered to the load will be from the combination of rectifier and inverter circuit. The main advantage of using Online UPS is that no switching is required between the main power line path and battery backup path in case of power outage.

Advantages of Online UPS

1. The Online UPS does not require switching between the two paths in case of power failure. Thus, the power delivered to the load will not be interrupted.
2. The significant advantage of using Online UPS is that the isolation between the load circuit and input circuit is proper, which is useful to get distortion-less signals.

In Online UPS the inverter is always in ON condition. Thus the power delivered to the load will be available at every instant of time, as there is zero transfer time.