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OPM_SGS_USM_M40_M50_2US_V010.doc
User Manual
SG Series 400 & 500 UL S2
4.3 PARALLEL SYSTEM OPERATION
4.3.1 Introduction to the parallel system
Two or more equal power units can be paralleled to increase the output power (paralleling for capacity)
or to improve the overall reliability of an UPS system (paralleling for redundancy).
The outputs of parallel units are connected to a common power bus, and in normal operation the units
connected on the parallel bus share the
Load
equally.
The modular concept of
SG Series 400 & 500
allows parallel operation of
up to 6 units
, without using
paralleling switchgear, external bypass circuits or common control circuitry (see
Fig. 4.3.1-1
).
Parallel units for power capacity
Several units can be paralleled in order to achieve output power greater than the maximum power of a
single unit.
The maximum total power shared between the paralleled units is equal to the
total installed nominal
power
.
In the event of a failure of one unit, the power supplied by the UPS system becomes insufficient and the
Load
will be transferred to the
Utility Bypass
source.
Parallel units for redundancy
The nominal power rating of the
n+1 out of n
redundant paralleled modules must be equal to or greater
than the required
Load
power.
The
Load
will be equally shared by the
n units
connected on the output bus.
Should one of the
n
paralleled units trip Off-line, the remaining (n+1) modules will supply the load,
maintaining conditioned power to the critical load.
From this results higher reliability and security for the
Load
plus a higher
MTBF (Mean Time Between
Failures)
.
Fig. 4.3.1-1 Block diagram parallel system operation
