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EATON Powerware
®
9315 UPS (200–300 kVA) Operatio n Manual S 164201036 Rev F powerware.com
Chapter 3 Understanding UPS Operation
The UPS functions automatically to supply AC electrical power to the critical load. The UPS
always operates in one of three modes:
Ī In Normal mode, the critical load is supplied by the inverter, which derives its power
from rectified utility AC power. In this mode, the rectifier also provides charging current
for the battery.
Ī In Bypass mode, the critical load is directly supported by utility power.
Ī In Battery mode, the battery cabinet provides DC power, which maintains inverter
operation. The battery supports the critical load.
The UPS continually monitors itself and the incoming u tility power, and automatically
switches between these modes as required, with no operator intervention. The
sophisticated d etection and switching logic inside the UPS ensures that operating mode
changes are automatic and transparent to the critical load. The UPS switches operating
modes in response to these system events:
Ī A command is an intervention that is externally initiated by an operator or by some site
action. A command causes the UPS to switch operating modes; it usually does not
require any further action by you.
Ī A notice is a minor system event that may or may not require your attention.
Ī An alarm is a system event that requires immediate operator intervention.
System events, alarm horns, and indicator lights are described in Chapter 10, “Responding
to System Events.”
3.1 Normal Mode
In Normal mode, utility AC power is supplied to the rectifier. The rectifier supplies DC
power to the inverter, which then supplies the critical load with AC power. The rectifier
also provides charging power to the battery. The battery charge condition is monitored by
the UPS and reported by a status indicator on the Monitor Panel. The message “System
Normal” appears in the status area of the LCD screen.
Figure 3-1 shows the path of electrical power through the UPS system when the UPS is
operating in Normal mode.