4.5 Wiring Parallel 93Pr Ups Systems; Power Wiring Overview - Eaton 93PR Series User And Installation Manual

4.5 Wiring Parallel 93PR UPS Systems

The outputs of multiple 93PR UPS systems can be connected in parallel. Up to four (4) units can be
paralleled. The UPS static bypass power rating needs to be identical among all paralleled units. However,
paralleled UPS cabinets can be housed with different number of UPM power modules.
The outputs are paralleled to increase the load capacity of the power system and for redundancy. The system
is paralleled for (N+1) redundancy, as long as there is always one or more UPS online than required to
support the load. The system is paralleled for capacity if all UPSs in a system are required to support the load.
Communication is required between the UPSs for system metering and mode control. System level
communication and control are accomplished using a Controller Area Network (CAN). A pull-chain signal in
each UPS, connected to the other UPSs in parallel and tied to the bypass Status Relay in each UPS, is used
for a secondary communication path. This arrangement ensures bypass control even if the CAN bus is lost.
Units with an internal MBS switch may not be connected in parallel.
4.5.1

Power Wiring Overview

Refer to Chapter 3.2.2 UPS system power wiring preparation for recommended cable and external fuse sizes
and installation practices.
Input Feed
The Input feed is defined as the power source connected to the UPS rectifier. The feed to all UPS's inputs
must be derived from the same source.
Bypass Feed
The Bypass feed is defined as the power source connected to the UPS Bypass. The feed to all UPS's bypass
must be derived from the same source. The shortest length of power wire from the source to the UPS must
be a minimum of 95 % of the length of the longest wire.
Output
The neutrals of all UPSs must be connected. The shortest length of wire from the source to the UPS must be
a minimum of 95 % of the length of the longest wire. The measurement is with respect to where the UPS's
outputs are tied.
dual Source
The Input Feed and Bypass feed may be separate sources. The sources must share a common neutral.
Battery connection
A separate battery shall be connected to each UPS, and the battery capacity for each UPS must be identical.
A common battery for all UPSs is not supported.
45
WARNING
25-75 kW
User's and Installation Guide