Rockwell Automation 1402-LSM Line Synchronization Module Installation Instructions - Manual (Page 29)

Chapter 3
General Operation
3–7
Load Sharing
The load sharing function allows multiple synchronizing buses to split the
load requirements on a power system based on the relative capacity of each
of the alternators. To use this function, the LSM must be configured with a
“Maximum Alternator Output Power” entry, a “Load Share Full–Scale
Voltage” entry, a “Load Share Deficit” entry, and a “Load Share Excess”
entry. The first entry specifies the maximum desired power output for the
alternator. The second entry specifies the load share output voltage that will
be created when the alternator is operating at maximum power. The third and
fourth entries define the regions where load sharing activity will take place.
The region between these two entries is the dead–band where no corrective
action takes place if the discrete inputs are being utilized for control. The
full–scale voltage is configurable to be between 2 and 4 volts.
The load sharing function is enabled when the “Load Share Disable” discrete
output from the PLC–5 is not asserted and the “Isochronous/Droop” discrete
output from the PLC–5 indicates isochronous mode. If new setup
information is received via block transfer while this function is enabled, load
sharing is terminated. The new configuration data is evaluated and normal
operation is resumed upon acceptance of the data.
The LSM provides a “Load Sharing Output” voltage that is resistively
coupled to the dual function input/output terminals. The magnitude of the
output voltage is calculated from the following formula:
(“Load Share Full–Scale Voltage”) (Actual Power) / (“Maximum
Alternator Output Power”)
The “Load Sharing Input” voltage is measured from the dual function
input/output terminals. The load sharing input is calculated by:
(“Load Sharing Input Voltage”) / (“Load Share Full–Scale Voltage”)
The “Load Share Error” is a fraction and is expressed as:
(Load Sharing Input Voltage) / (Load Share Full–Scale Voltage) – (Actual
Power) / (Maximum Alternator Output Power)
If the error is negative, the alternator is supplying too much of the load
requirements and the “Reduce Power – load share adjust” discrete input to
the PLC–5 is asserted when the error exceeds the “Load Share Excess” entry.
If the error is equal to zero, the load is being properly shared. If the error is
positive, the alternator is not supplying enough of the load requirements and
the “Raise Power – load share adjust” discrete input to the PLC–5 is asserted
when the error exceeds the “Load Share Deficit” entry.
The LSM load sharing circuit is isolated from the external circuitry whenever
load sharing is disabled, droop mode is indicated, or if power is removed
from the module.
Operational Characteristics
Continued