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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
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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.
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.
OPM_SGS_USM_10K_40K_0US_V010.doc | 15/88 | Operating Manual SG Series 10, 20, 30 & 40 kVA |