TS_604_01 PowerWave PW3000/TP User Manual UK 5/1/18
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3: Installation
3.6.2 UPS Cable and fuse sizing
3.6.3 Power cabling for a parallel system
In order to achieve equal load sharing between the UPS cabinets in a parallel system, the length of the input cables from
the input distribution board to each cabinet should be as equal as possible, with a maximum difference of 20%. This also
applies to the UPS output cables. Each module should be connected to an output circuit breaker located on a switch panel
no further than 20 meters from the cabinets.
External maintenance bypass
Figure 3.4 External bypass circuit
An external maintenance bypass facility, such as that shown in Figure 3.4, can be installed to increase the system
flexibility. This circuit allows an individual module to be isolated from the system, for repair or total replacement, by
opening its input fused isolator and Output Breaker. It also allows the total system to be bypassed by closing the System
Bypass Breaker and opening the System Output Breaker; which in turn allows testing of the entire parallel system.
When such an external maintenance bypass is used it is crucial that the UPS modules are all operating on bypass (or
internal maintenance bypass) before the System Bypass Breaker is closed, to avoid the possibility of module damage. For
this reason it is usual to incorporate some form of safety interlocking mechanism around the external breakers.
Key Point:
The information in figures 3.8 and 3.9 is given for guidance only:
•
Fuse and Cable recommendations are to IEC 60950-1:2001.
•
All external fuses, isolators and power cables must be rated and installed in accordance with the
prescribed IEC standards or local regulations:
– e.g. BS7671: 2008 incorporating amendment No.1:2011.
•
External DC Cables and battery fuses are bespoke to the installation.
UPS 1
UPS 2
UPS 3
UPS 4
MAINS / BYPASS
System
Output
Breaker
System
Input
Breaker
UPS 1
Input/bypass
Isolator
UPS 2
Input/byp
Isolator
UPS 3
Input/byp
Isolator
UPS 4
Input/byp
Isolator
UPS 1
Output
Breaker
UPS 2
Output
Breaker
UPS 4
Output
Breaker
UPS 3
Output
Breaker
To Load Dist. Panel
System
Bypass
Breaker
