Powerware 9315s - Manual (Page 57)

7--5 Powerware 9315 Parallel Capacity/Redundant System with PHP SSBM
164201373 Rev. A 092402
7.2.2 Bypass Mode
The SSBM automatically switches to Bypass mode if it detects a UPM overload,
UPMs unavailable, load fault, or internal failure. The bypass source supplies the
commercial AC power to the load directly.
CAUTION:
The critical load is not protected while the SSBM is in Bypass mode.
Figure 7---2 shows the path of electrical power through the Parallel
Capacity/Redundant system when operating in Bypass 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---2. Path of Current Through the Parallel Capacity/Redundant System
in Bypass Mode.
You can transfer the SSBM from Normal mode to Bypass mode manually.
However, the SSBM switches automatically to Bypass mode whenever the UPMs
can no longer supply the critical load. If the SSBM transfers to Bypass mode from
Normal mode due to an output voltage deviation, the SSBM automatically attempts
to transfer back to Normal mode (up to three times within a 10-minute period).
The fourth transfer or an overload condition will lock the critical load on the bypass
source and requires operator intervention to transfer.
Bypass mode is a normal operating mode, and not an alarm condition. However, if
the SSBM is unable to return to Normal mode following an automatic transfer to
Bypass mode, an alarm condition will be recorded.