Powerware 9315s - Manual (Page 58)

7--6 Powerware 9315 Parallel Capacity/Redundant System with PHP SSBM
164201373 Rev. A 092402
7.2.3 Battery Mode
The UPMs transfers to Battery mode automatically if a utility power outage occurs,
or if the utility power does not conform to specified parameters. In Battery mode,
the batteries provide emergency DC power that the inverters convert to AC power.
When the UPMs switch to Battery mode, the alarm indications depend on the
cause and condition of the battery charge. The length of time the system can
operate in Battery mode depends on loading and the battery supply capacity.
Figure 7---3 shows the path of electrical power through the Parallel
Capacity/Redundant system when operating in Battery mode.
UPM1
UPM2
UPM3
UPM4
SS
FBP
CBP
CBS
BYPASS
INPUT
OUTPUT TO
CRITICAL
LOAD
BATT
UPM
INPUT
BATT
BATT
BATT
SSBM
Path of Electrical Power
(open)
Figure 7---3. Path of Current Through the Parallel Capacity/Redundant
System in Battery Mode
When the discharging battery voltage reaches the lower limit of UPM operational
capability, the critical load is transferred by the SSBM to Bypass mode, if it is
available. If Bypass input is not available, a “Shutdown Imminent” warning occurs.
The warning time before critical load loss occurs is approximately 2 minutes,
depending on battery capacity and the amount of loading.
If incoming power returns to within specified parameters, the UPMs automatically
return to Normal mode and alarm indications clear. However, the process of
returning to Normal mode is not instantaneous. The UPMs gradually draw
increasing power from the incoming utility until Normal mode is achieved.