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IV. PARALLEL OPERATION
4.1 Introduction
Two (or more) identical PDSP series UPSs can be interconnected for parallel operation.
The main purposes for parallel use of PDSP series UPSs are:
-Redundancy for Increased Reliability
-Power Increase
Although recent UPS designs are perfect and have high MTBF figures, a second (or more) UPS can be used
in parallel with the first one, for supplying the critical load in case of any possible failure of the first UPS. In
such an application the faulty UPS is isolated automatically from the parallel system and the other UPS (or
UPSs) continues to supply the critical load. Use of Redundant UPSs in parallel, therefore, provides increased
reliability for the critical load connected to the parallel system output.
If power demand increases in a certain UPS application exceeding the power rating of an already installed
stand-alone UPS, a second (or more) UPS of the same model and power rating can be added in parallel to the
existing UPS to increase the output power capacity.
Schematic diagram of parallel connection of two PDSP series UPS units is shown in Figure 4.1
3 PHASE
MAINS I/P
3 PHASE
AC Output
Rectifier /
Charger
Battery
(Dual Polarity)
Maintenance
B
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