Parallel redundant & power system UPS 60…800kVA FXS – Operating manual
Sistema parallelo ridondante e di potenza UPS 60…800kVA FXS – Manuale operativo
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JUD413937
Rev.A JSE414215 07/06/11
3.
REDUNDANT PARALLEL SYSTEM
3.1 DESCRIPTION
PARALLEL REDUNDANCY SYSTEM
The parallel redundancy system is constituted by “N” UPS (up to a maximum of 5+1
units), configurated as redundant parallel units. In the UPS The Manual Bypass is
external and optional, and generally is only one for all units.
In addition to the standard functions of a UPS such as power continuity, protection of
the load from mains distortions etc., the parallel redundancy system guarantees a
continuity of power even if more than one system failure is ascertained.
This is possible because all the units are constantly operative and feed the load in
parallel, furnishing each with a current equal to “total load /n”, where “n” is the number
of the units that are being supplied at that moment.
The automatic distribution control of the AC current equalizes the currents of the “n”
units and reduces the unbalance to less than 10%, under all load conditions.
The load is fed by the parallel inverters even when an instantaneous overload
“n x
200%” of the nominal load of every individual unit is verified.
In the event of a breakdown of one of the units, the load is fed by the others. Only in
the event that ulterior breakdowns are verified in the other units will the load be
transferred to the Emergency Mains (Bypass).
3.2
OPERATIONAL STATUS PARALLEL REDUNDANCY
If a breakdown occurs for which a UPS can no longer distribute on the load, during
the state of “n UPS in normal functioning”, the parallel redundancy system gets
transferred to the “n-1 UPS in normal operational status. Under these conditions, a
further irregularity of a UPS which prevents the feeding of the load, transfers the system
to the “Emergency Bypass Line, feed the load” condition, every additional irregularity,
may or may not, according to the type of irregularity, interrupt the feed to the load. The
irregularies are registered by each UPS with alarms and visualized on the same front
panel of the UPS.
In the event that a system mode has a rectifier breakdown or mains loss, in the “n
UPS in normal functioning”, the UPS will continue to distribute the load discharging the
battery, automatically isolating itself from the system until the end of the back-up time
and transfers the system to the “n-1” UPS normal operating mode.
If the system is transferred to the Manual Bypass (MB), the load gets fed directly
from the mains, therefore not guaranteeing the continuity of the load and the entire
parallel system becomes separated from the load.