Powerware 9390 UPS 100160 kVA - Manual (Page 62)

UNDERSTANDING UPS OPERATION
EATON Powerware ® 9390 UPS (20–80 kVA) Installation and Operation Manual S 164201603 Rev 2 www.powerware.com 7-10
7.2.3 Bypass Mode – Parallel
In Bypass mode, the output of the system is provided with three-phase AC power
directly from the bypass input. While in this mode, the output of the system is not
protected from fluctuations, spikes, or power outages from the source. No power
filtering, conditioning, or battery support is available to the output of the system in the
Bypass mode of operation.
The parallel system automatically switches to Bypass mode if it detects a UPM
overload, UPMs unavailable, load fault, or internal failure.
Figure 7‐6 shows the path of electrical power through the parallel system when
operating in Bypass mode.
Main Power Flow
UPM 1
UPM 2
UPM 3
UPM 4
Output to
Critical
Load
Battery
UPM Input
Module Tie Cabinet
UPM 1 Output
Bypass Input
UPM 2 Output
UPM 3 Output
UPM 4 Output
Battery
Battery
Battery
Closed
Open
Breakers
Figure 7‐6. Path of Current through the UPMs in Bypass Mode – Parallel
In a parallel redundant or capacity type system, each module operates similar to a
single module, but in parallel with each other. The bypass source for the load is
derived from the bypass input of one, two, three, or four modules, depending on the
system configuration through the internal continuous-duty static switches. If a module
is taken offline, the other modules remain online to support the load. If more modules
than can support the load must be taken offline, the load must be transferred to
maintenance bypass or shut down.