True on-line UPS units provide the highest level of protection. An on-line UPS absorbs the incoming AC supply, converts it to DC then inverts it to AC to supply critical power loads. An inverter supplies regulated AC power to loads at all times; either from rectified mains or a battery with an on-line UPS.In the event of a blackout, there is no transfer time or break in power supply.
Most on-line UPS units contain an automatic bypass to ensure continuous power supply during a short-term overload or UPS failure. They are ideal for critical loads, sensitive equipment such as medical or scientific technology and industrial loads. All on-line UPS units are fully generator compatible.
These UPS units are often referred to as double conversions because they can convert from AC–DC to DC–AC.