Powerware 9315 Installation & Operation Manual page 23

Under normal operating conditions, bypass sensing voltage from the slave system
is provided back to its own inverter through the Powerware Fixed Master Sync
Control. As long as the bypass sources feeding the slave system and the master
system are available and in-phase with each other and the master critical load is in
phase with its own bypass, the slave system remains synchronized with its own
bypass source and the two systems remain synchronized with each other. If the
slave system's bypass becomes out of phase with the master system bypass
(>0.1 Hz apart), the master critical load loses sync with its own bypass, or one or
both sources become unavailable, the Powerware Fixed Master Sync Control
provides a new synchronization reference to the slave system. The slave system's
new reference is provided by the Powerware Fixed Master Sync Control from the
output (critical load) bus of the Master system (See Figure 12).
When the two bypass sources regain availability and synchronization and the
master critical load remains in sync with its bypass, the Powerware Fixed Master
Sync Control provides the slave system with its own bypass sensing voltage as a
synchronization reference. Before re-synchronization occurs, a fifteen second
preset time delay has been provided to ensure the two bypass sources maintain
acceptable synchronization.
In order to maintain a fault tolerant arrangement, fault conditions or abnormal
operating conditions are accounted for in the Powerware Sync Control. The main
provisions are listed below:
1.
When the Slave system is synchronized to the master source, a transfer to
bypass disable signal is sent to the slave system. This inhibits any transfers to
bypass on the slave system.
2.
If either of the systems or both loses its critical load bus voltage sensing, the
slave system synchronizes to its own bypass source.
3.
Dual redundant logic power supplies are incorporated within the Powerware
Fixed Master Sync Control, ensuring the slave system remains synchronized
with the master even during the loss of one of the logic power supplies. If one
or both power supplies fail, an alarm is sent back to the slave system
indicating a "SYNC CONTROL TROUBLE" alarm. These power supplies are
powered from each system's critical load bus.
4.
With a complete loss of logic power to the Powerware Fixed Master Sync
Control (due to either component failure or power supply fault), the slave
system synchronizes to its own bypass source.
Powerware 9315 Fixed Master Sync Control
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