Modifications reserved
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OPM_SGS_USM_M40_M50_1US_V020.doc
Operating Manual
SG Series 400 & 500 kVA
3.2.3 Utility recovery operation
As soon as the AC input power recovers, the
Rectifier
will
start automatically, supplying DC power to the
Inverter
and recharging the
Battery
.
If the
Inverter
was previously shut down due to low
Battery
, the
Load
will be initially powered by
Utility
through the
Automatic Bypass
.
When the
Battery
is recharged enough to ensure a
minimum time of operation with the present load, the
Inverter
will start automatically and the
Load
will be
transferred back to the
Inverter
.
Fig. 3.2.3-1 Block diagram Utility recovery operation
In case of parallel operation
When the AC input power recovers,
the Rectifiers will start up sequentially,
according to their
number in the parallel system. This minimizes the
initial inrush current.
The
Inverters will start up automatically
, but only when the Battery has recharged enough for a
minimum runtime
with the present load.
When
enough Inverters to supply the Load have been restarted,
the Load will be transferred from the
Automatic Bypass back to the Inverter output.
3.2.4 Automatic Bypass
In normal operation, the
Load
is supplied by the
Inverter
.
When the control system detects a fault in the
Inverter
,
an overload condition or a short-circuit condition, the
Automatic Bypass
will transfer the critical
Load
to the
Utility
without interruption.
When the
Inverter
recovers, or the overload or short-
circuit condition is corrected, the
Load
will be
automatically transferred back to the
Inverter
.
If the UPS is unable to return to normal mode following
an automatic transfer to
Bypass mode
, an alarm
condition will be initiated.
A
Manual Bypass
(operator initiated) will not be
considered as an alarm condition.
Fig. 3.2.4-1 Block diagram Automatic Bypass
In case of parallel operation
Each unit has it’s own internal Bypass. These units are continuously exchanging information, enabling
all of the internal Bypass circuits in a parallel system to operate simultaneously.
If the Inverter of a unit fails, it’s Bypass circuit remains available to the parallel system.
It is excluded only if the unit is separated from the common bus by opening it’s output switch
Q1
.
3.2.5 Manual Bypass
The
Manual Bypass
circuit consists of
Q1
and
Q2
manual
switches, which permits transfer of the
Load
directly to
the unconditioned AC power without interruption, leaving
the UPS available for maintenance.
Fig. 3.2.5-1 Block diagram Manual Bypass
