GE Industrial Solutions SG Series 50 & 80 kVA Operating Manual - Manual (Page 15)

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OPM_SGS_USM_50K_80K_0US_V030.doc Operating Manual SG Series 50 & 80 kVA
3.3.2 Features of RPA parallel system
The SG Series parallel system is designed to provide a complete Redundant Parallel Architecture, and
is free from common equipment.
Not only the Inverters are redundant, but also the Bypass functions are designed with redundant
modular concept.
When one UPS needs maintenance or service, the Load is powered by the other units supplying the
Load bus.
The redundant communication bus to which all units are connected keeps each unit informed about the
status of all the other units.
The control panel located on each unit allows controlling and monitoring the status of this unit.
3.3.3 System control
A high-speed redundant, serial communication bus guarantees the exchange of data and thus the
communication between the CPU's of each unit.
Each module controls it's own function and operational status and communicates with all other
modules, in order to act or react if necessary, adapting it to the new conditions.
3.3.4 Synchronization
All units are identical, but one unit is arbitrarily selected as the reference and all the other units
synchronize to this unit, which in turn, synchronizes to the Utility Bypass voltage, as long as the later is
within tolerances.
In case of reference failure, another unit in the parallel system is automatically chosen to take over the
reference role.
The Bypass Input for all the units of the parallel system must be supplied from the same AC source (no
phase shift allowed between them).
3.3.5 Load sharing
On each unit of the parallel system, Inverter Output Voltage and Current are measured and applied to a
Load sharing bus.
An eventual difference between the units is therefore automatically equalized.
NOTE !
It is strongly recommended that no transformers, automatic circuit breakers or
fuses should be inserted between the unit’s output and the Load common bus bars.
However, it is recommended that a disconnect or isolation switch be inserted.