Line Interactive UPS

A line interactive UPS contains a regulator that boosts the mains power supply when it falls. It can regulate power to an acceptable level, without the use of a battery, during a brownout or surge in supply voltage. They protect the critical system against blackout, brownouts, spikes and sags

There is a short period (ie transfer time) when a line interactive UPS will switch to battery mode during a blackout. Most line interactive UPS units have additional features including shutdown software and telephone line protection. They provide a high level of protection, at an affordable price.

On-Line UPS

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 via a battery. On-line UPS systems isolate the critical load from the mains at all times and will protect against all bad power situations including b lackout, brownouts, spikes, sags, RF noise, harmonics and surges.

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.