Powerware 650825 kVA operation manual Normal Mode Distributed Bypass

UNDERSTANDING UPS OPERATION

The UPSs continually monitor themselves and the incoming utility power and automatically switch between these modes as required, without operator intervention, except when manually switching to Bypass mode. The sophisticated detection and switching logic inside the UPSs ensures that operating mode changes are automatic and transparent to the critical load, while internal monitoring systems indicate the current mode of operation. The UPSs switch operating modes in response to these system events:

SA command is an intervention that is externally initiated by an operator or by some site action. A command causes the UPSs to switch operating modes; it usually does not require any further action.

SA notice is a minor system event that may or may not require attention.

SAn alarm is a system event that requires immediate intervention.

The following paragraphs describe the differences in the three parallel system operating modes, using block diagrams to show the power flow during each mode of operation.

6.4.2Normal Mode – Distributed Bypass

In Normal mode, utility AC power is supplied to the UPSs. Each UPS then conditions the incoming AC power and provides clean, regulated AC power to tie cabinet or distribution panel for parallel systems up to four modules. The applied load is shared equally among the available UPMs in the system.

Figure 6-18shows the path of electrical power through the parallel system when operating in Normal mode.

Bypass Input	UPS Input
	UPS 1
Battery
	UPS 2
Battery
	UPS 3
Battery

UPS 4

Battery

Breakers

Closed

Main Power Flow

Open

Tie Cabinet

UPS 1 Output

UPS 2 Output

UPS 3 Output

UPS 4 Output

Output to

Critical Load

Figure 6-18. Path of Current through the UPSs in Normal Mode – Distributed Bypass

6−22 EATON Powerware® 9395 UPS (650–825 kVA) Installation and Operation Manual S 164201725 Rev 2 www.powerware.com