Powerware 9395 UPS and Plus 1 UPS 650825 kVA - Manual (Page 135)

UNDERSTANDING UPS OPERATION
EATON Powerware ® 9395 UPS (650–825 kVA) Installation and Operation Manual S 164201725 Rev 2 www.powerware.com 6−23
If the utility AC power is interrupted or is out of specification, the UPSs automatically
switch to Battery mode to support the critical load without interruption. When utility
power returns, the UPSs return to Normal mode.
If the UPSs become overloaded or unavailable, the distributed bypass system
switches to Bypass mode. The distributed bypass system automatically returns to
Normal mode when the overload condition is cleared and system operation is
restored within specified limits.
6.4.3 Bypass Mode – Distributed Bypass
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 battery
support is available to the output of the system in the Bypass mode of operation.
The distributed bypass system automatically switches to Bypass mode if it detects a
UPS system overload or load fault.
If one UPS becomes unavailable, the distributed bypass system dynamically updates
the redundancy calculation to determine if the remaining UPSs can support the load.
If the load can be supported, the system does not switch to bypass.
Figure 6-19 shows the path of electrical power through the parallel system when
operating in Bypass mode.
Main Power Flow
UPS 1
UPS 2
UPS 3
UPS 4
Output to
Critical Load
Battery
UPS Input
Tie Cabinet
UPS 1 Output
Bypass Input
UPS 2 Output
UPS 3 Output
UPS 4 Output
Battery
Battery
Battery
Closed
Open
Breakers
Figure 6-19. Path of Current through the UPSs in Bypass Mode – Distributed Bypass