Powerware 9315 - Manual (Page 40)

34 Powerware 9315 Parallel Redundant System I & O
164202013, Rev. D 041599
Normal, Battery, and Bypass Modes with Parallel Operation
With the parallel redundant system, there are operating mode differences. These
differences primarily deal with the way transfers to and from bypass are handled.
When both UPS modules are in Normal mode, the parallel redundant system
functions normally to supply clean, filtered power to the critical load. The AC
output of the UPS modules feed the clean power to its designated MOB in the
parallel cabinet. In Normal mode, the MOBs are closed and power continues to
the AC output (critical bus) of the parallel cabinet, supporting the critical load.
When there is a power outage or some disturbance in the utility, the UPS modules
automatically switch to Battery mode. In Battery mode, the battery supplies power
to the critical load as in normal UPS system operation. The only difference is that
the critical bus in the parallel cabinet is the AC output. See the PowerwareÒ 9315
Operation manual provided with the UPS system for details on Battery mode of
operation.
When both UPS modules are in Bypass mode, utility power directly supports the
critical load as is normal in UPS system operation.
When one UPS module becomes disabled and the redundant module is in Normal
mode, the disabled module shuts off rather than transfer to Bypass. The redundant
module continues to supply power to the critical load. Bypass is only activated if
the critical bus in the parallel cabinet fails to recover within a quarter cycle of the
initial disturbance.
If a manual transfer to Bypass mode is initiated while the redundant module is in
Normal mode, the module to be transferred to Bypass simply shuts off.
If both UPS modules are in bypass and their mode switches are in the Normal
mode position, activate the key switch on either UPS module and both modules
transfer to Normal.
If one UPS module is in Normal mode and the redundant module is in Bypass
mode, the following sequence will take place:
·
The module in Bypass will automatically try to transfer to Normal mode
· If unable to transfer to Normal mode, the redundant module will try to
automatically clear itself from Bypass
· If the redundant module is unable to clear itself from Bypass, the module in
Normal mode will wait ten (10) seconds and then transfer to Bypass.