Manual 37443A DSLC-2 - Digital Synchronizer and Load Control
© Woodward Page 165/226
Soft Loading Into A Load Sharing System
The mode for automatic soft loading into a load sharing system is selected with an open “Base Load” contact in-
put, terminal 73. The “Load/Unload” input, terminal 74, activates the soft loading function after the oncoming
generator set is properly synchronized and the paralleling generator breaker closes, which also closes the genera-
tor “CB Aux” contacts to terminal 70. When the “CB Aux” contact is closed with the “Base Load” and
“Load/Unload” inputs open, isochronous load sharing mode at zero load is automatically selected. If the unit is
the only one with a closed breaker in a load sharing system the “Load/Unload” input is ignored and the generator
runs purely frequency controlled.
If the “Load/Unload” contact input was closed when the “CB Aux” contact was closed, the soft loading ramp will
be started immediately. Otherwise, load sharing at zero load will continue. When the loading ramp is activated,
the soft loading function compares the load on the oncoming unit with the load on the load sharing system. The
load ramp then linearly increases the load on the unit at the rate set by the load ramp rate setpoint. When the
loads match, the ramp is shut off. In the case of an unloaded system or when derated shared load is below the un-
load trip level, the unit enters load sharing without the ramp function. The pause command may be used to hold
the ramp if desired.
Load sharing
Load sharing becomes active when
• CB Aux input is closed
• Load / Unload input is closed
Adjustments when in load share mode
• PID frequency trim
o Frequency trim proportional gain (parameter 5510)
o Frequency trim integral gain (parameter 5511)
o Frequency trim derivative ratio (parameter 5512)
• Load share gain
• Load share factor
• Load ramp rate
• Unload ramp rate
Soft Unloading From A Load Sharing Or A Base Loaded System
The unload sequence is initiated by opening the “Load/Unload” contact. The DSLC-2 control then ramps the load
down to zero at the preset rate. When the load reaches the unload trip level setpoint, the “Breaker Open” relay,
terminal 47/48, is momentarily deactivated to initiate the opening of the generator breaker. This command can be
used to separate the engine generator set from the paralleled system.
Load sharing – unload
• Unload ramp rate
• Unload trip level
• Unload trip time
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