About Uninterruptible Power Supplies (UPS)
What are the different types of UPSs and how do they differ?
There are basically three types of UPSs: Standby, Line-interactive,
Standby: (sometimes called "off-line") With this type of
power supply, power comes directly from the A/C outlet until the voltage sags or the power
fails. After the power sags or fails, a battery powered inverter almost immediately turns
on to continue to supply you with power. Batteries are charged, as necessary, when direct
A/C power is available. Even while power is coming directly from the A/C outlet, the UPS
provides protection from voltage spikes and surges. Standby units are the low cost
solution in the UPS family.
Line-interactive: Just like the standby units, line-interactive
UPSs provide protection from spikes and surges, as well as supplying auxiliary power if a
voltage sag or a blackout occurs. Unlike the standby units, line-interactive UPSs provide
automatic voltage boost when the power dips, without accessing the batteries. This feature
provides continuous lined conditioning, promotes longer battery life, and eliminates
electronic "noise" that can cause minor application errors and loss of data.
On-line: On-line UPSs provide the highest quality of power
protection by using a double-conversion technique. The UPS takes the incoming A/C power
and recreates it by converting the voltage to D/C, then conditioning the power to
eliminate noise, sags, or surges, and, finally, converting it back to A/C before it exists
the UPS. Since the power runs continuously through the inverter, there is no transfer or
switching time to battery mode in the event of a blackout.