20 - 80 kVA parallel UPS systems
User’s and Installation Manual
1018390
Revision C
9
3.2 Theory of operation
A double conversion on-line UPS conditions the raw mains and supplies continuous, clean
three-phase power to the critical systems. It keeps the battery constantly charged while
feeding the critical load. The UPS will continue to supply clean power without any
interruption at the output even at mains failure. It will shut down in order to prevent a total
discharge of the battery if the power failure outlasts the backup time of battery bank. The
UPS will start up again automatically, providing power to the critical load and charging the
battery bank, when the mains voltage is restored.
Figure 3a.
Block diagram of UPS module
A double conversion UPS provides the best protection for computer systems and other
intelligent devices such as measurement instruments and industrial automation applications.
UPS modules incorporate digital signal processing technology to monitor and control its
own operation. They protect different types of sensitive electrical devices such as
computers, workstations, banking systems, sales terminals, critical instrumentation,
telecommunications systems, process control systems, hospital equipment, etc.
Figure 3b.
Functional components of UPS module
