GE Industrial Solutions SG Series 100 – 120 – 150 kVA Operating Manual - Manual (Page 13)

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OPM_SGS_USM_M10_M15_0US_V030.doc Operating Manual SG Series 100 – 120 - 150 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