Powerware 9315s - Manual (Page 53)

7--1 Powerware 9315 Parallel Capacity/Redundant System with PHP SSBM
164201373 Rev. A 092402
Understanding Parallel
Capacity/Redundant System Operation
The Switchboard System Bypass Module (SSBM) supports the normal operation of
the Powerware 9315 Parallel Capacity/Redundant system by offering parallel
capacity/redundant capability. The Parallel Capacity/Redundant system continues
to maintain power to the critical loads during commercial electrical power
brownout, blackout, overvoltage, undervoltage, and out-of-tolerance frequency
conditions. Refer to Figure 164201373---3 in Appendix A of this manual for the
detailed relationship of the SSBM and the UPMs.
If utility power is interrupted or falls outside the parameters specified in the
Powerware 9315 Operation manual, the Parallel Capacity/Redundant system uses
a backup battery supply to sustain power to the critical load for a specified period
of time or until the utility power returns. For extended power outages, the backup
battery supply allows you to either transfer to an alternate power system (such as a
generator) or shut down the critical load in an orderly manner. Refer to the
Powerware 9315 Operation manual provided with the UPMs for operation of the
UPMs.
7.1 Looking Inside the Parallel Capacity/Redundant
System
The output of the system is normally supplied by several Uninterruptible Power
Modules (UPMs). Multiple UPMs are connected with their outputs in parallel to
provide a load level greater than the rating of one UPM and for redundancy . The
paralleled UPMs supply the output load with protected power as long as the load
does not exceed the combined rating of the paralleled UPMs.
The power system is denoted redundant as long as one of the UPMs can be
disconnected from the output bus and the remaining UPMs can continue to supply
power to the load without exceeding their ratings.
The SSBM, contains switchgear and components that allow the the UPMs to be
paralleled and the source of system output power to be transferred between
Bypass and the paralleled UPMs .
When the load is being supplied by the UPMs, the system output bus is
continuously monitored by the SSBM for an over or under voltage condition. If an
out of limits condition is detected, the SSBM will transfer the load to bypass using a
high speed emergency bypass. The transfer will occur in less than 4 milliseconds.
The emergency bypass consist of a static switch, a wraparound bypass breaker
(CBP) and a backfeed protection breaker (FBP). The backfeed protection breaker
is located in series with the static switch. If an SCR shorts, the breaker will open so
that the UPMs will not backfeed the bypass source, dropping the load when a utility
outage occurs.
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