Figure 4-7 . Principle Of Paralleled Ups Systems - Eaton 93PR Series User And Installation Manual

MOB's
Module Output Breakers (MOBs) allow the output of the UPS to be disconnected from the other UPSs
and system load for maintenance and service. Design considerations assume that each UPS has a Module
Output Breaker (MOB). The breaker shall not disconnect neutral.
The MOB must have a "N.C" auxiliary contact. The N.C contact is connected to the "signal inputs" which is
at the top of the dead front in the ups. If the MOB is open, the "N.C" contact will also be open so as to open
the Pull-Chain signal.
Figure 4-7: Principle of paralleled UPS systems shows the principles of paralleled UPS systems with MOBs
MOB Override
Users without MOBs installed can simply leave the MOB signal input disabled. The user should be aware
that systems without MOB have limited maintenance capability.
Parallel system wiring
Figure 4-7: Principle of Paralleled UPS Systems
Required parallel system wiring length must be equal to ensure approximately equal current sharing when in
Bypass Mode.
For proper operation the following must be true: 1A+1B=2A+2B=3A+3B=4A+4B.
Any difference in wire length will result in decreased capacity and improper operation of the UPS system
while on bypass.
25-75 kW
User's and Installation Guide 46