A Little UPS 101 For Those Who Need a Refresh or Are Learning For the First Time.

There are generally five types of Uninterruptible Power Supplies (UPS) systems that are used. They are:

Standby UPS
Line-interactive UPS
Standby-ferro UPS
Double conversion online UPS
Delta conversion online UPS

The types are based on a demand for an AC power backup for the load. The standby UPS is a configuration in which a battery backup is charged by the line voltage and is fed through an inverter to a transfer switch. When the prime power is lost, the transfer switch brings the standby power path online.
The line-interactive UPS is one of the most commonly used designs for an uninterruptable power supply. It detects voltage fluctuations and acts as a backup power source during blackouts and brownouts.
The standby-ferro UPS uses a transformer to supply power to the load when the input voltage falls outside of predetermined limits.
The double conversion online UPS is a configuration in which the battery backup is always online. The inverter supplies power to the load whether or not the utility power is present.
The delta conversion online UPS is similar to double conversion online UPS but it has an additional converter that provides better efficiency and reliability.