External Parallel Ups System Power Wiring Preparation - Eaton 93PM UPS Installation And Operation Manual

The bypass feed into this equipment uses four wires. The rectifier feed into this equipment uses three
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wires. The phases must be symmetrical about ground (from a Wye source, phase rotation clockwise A, B, C)
for proper equipment operation.
If installing an external maintenance bypass, all feeds to the UPS including the Rectifier Input Breaker (RIB)
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(if installed) must have a service disconnect independent of the maintenance bypass power path. Most
maintenance bypass solutions provide UPS input feeds derived from but isolated from the maintenance
bypass power path. If the maintenance bypass solution being installed does not provide such functionality,
DO NOT use a single feeder breaker to supply both the UPS and the maintenance bypass.
3.2.3

External Parallel UPS System Power Wiring Preparation

Read and understand the following notes in addition to the notes in paragraph 3.2.2 while planning and
performing the external parallel installation:
All external parallel UPS rectifier inputs must come from one source and all bypass input feeds must come
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from one source.
All UPSs in the external parallel system must contain the same number of UPMs. Mixed UPS kVA ratings
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are not permitted.
External parallel UPS input wiring size requirements and output wiring size requirements from the UPSs to
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the tie cabinet are the same as listed in Table 3-4.
The tie cabinet must contain Module Output Breakers (MOBs) with dual auxiliary contacts for control of the
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system. Without dual auxiliary MOBs, UPMs are not allowed to go to bypass individually during servicing.
All UPMs will go to bypass instead of the just the UPM needing service, decreasing critical load protection.
With dual auxiliary MOBs, one UPM can be bypassed while the remaining UPMs support the load as long as
the remaining UPMs have the capacity to do so.
External parallel system wiring length should be in accordance with Figure 3-9, to ensure approximately
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equal current sharing when in bypass mode.
Eaton 93PM UPS (20–50 kW, 480V Four Wire – 50 kW Frame) Installation and Operation Manual P-164000540—Rev 4
UPS Installation Plan and Unpacking
www.eaton.com/powerquality 3-13