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3.9
RPA PARALLEL SYSTEM CONNECTION
WARNING !
This operation must be performed by QUALIFIED SERVICE PERSONNEL ONLY before
the initial start-up.
ENSURE THAT THE UPS INSTALLATION IS COMPLETELY POWERED DOWN.
3.9.1 Power wiring of parallel units
To guarantee good Load sharing between the units of a Parallel System, we recommend that the cable
length from the input distribution board (5) to the output distribution board (9) is equal for each unit (a+b
= c+d = e+f = g+h = i+l = m+n). Tolerance: +/- 10%.
The RPA Cable Saver option introduces a Bypass Inductor in every UPS module, reducing the influence of
external conductor length on bypass current sharing.
The RPA Cable Saver option may extends the cable length tolerance to +/-25% for runs not exceeding
160 feet (49m).
For details of the RPA Cable Saver option and further recommendations on power wiring and system
connections, please contact your Service Center, which will help you find cost effective solutions.
The AC input power of the Bypass must be the same for all units of the parallel system - no phase shift
allowed between units.
NOTE !
It is strongly recommended that no transformers, automatic circuit breakers or
fuses be inserted between the unit's output and the Load common bus bars.
However, it is recommended that a disconnection or isolation switch be installed in
order to totally isolate a unit if needed.
Verify that power wiring and control wiring are run in separate conduits or cable trays.
UPS input cables must be run in separate conduits from the output cables.
Fig. 3.9.1-1 Power wiring of RPA Parallel System
Modifications reserved
OPM_SGS_ISG_M40_M50_2US_V021.doc
1
= Rectifier
2
= Inverter
3
= Automatic Bypass
4
= Manual Bypass (option)
5
= Input Utility Distribution
6
= Unit Output Load
7
= External Battery fuse or MCB
8
= External Battery
Common bus bar and Output
9
=
Load Distribution
= UPS Number 1
2
= UPS Number 2
3
= UPS Number 3
4
= UPS Number 4
5
= UPS Number 5
6
= UPS Number 6
User Manual SG Series 400 & 500 UL S2
Page 32/41
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