TUBE A. 3S3426 - Caterpillar

Droop Adjustment
This adjustment is only necessary for droop operation. The DROOP control sets the amount of speed regulation for the engine. The droop adjustment is only required when paralleling with utility bus or other units which are using hydromechanical governors. Since speed regulation is a function of load or power delivered, the DROOP function makes a reduction to the engine speed setting with an increase in load. The percent of speed droop is the difference between engine speed at "No Load" and engine speed at "Full Load". The percent of speed droop is expressed as a percentage of full load speed. It is calculated as follows.(No Load Speed - Full Load Speed) ? 100 / Full Load Speed = Percent of Flow LossExample
(61.8 Hz - 60 Hz) ? 100 / 60 Hz = 3 Percent DroopNormally, the percent of droop is known. The correction that is needed is the amount to increase the "No Load" setting. In this case, the "No Load" setting is calculated as follows. (100 percent + Percent of Droop) ? Full Loading Setting = No Loading SettingNote: If only 50 percent loading is possible, a "No Load" setting of 60.9 Hz would be an indication of three percent droop as shown in the Illustration 1.
Illustration 1 g00617347
Droop AdjustmentSetting Droop On System Operating Into A Commercial Bus
With the unit off the line, run the engine. Set the speed to 60 Hz ("No Load" setting). Mark this position.
Set RATED SPEED or external Speed Trim potentiometer setting above the 60 Hz reference by the percent droop required. For example, three percent droop would mean raising the speed to 61.8 Hz. Mark this potentiometer position. Return the potentiometer to 60 Hz.
Turn the "DROOP" potentiometer fully clockwise (maximum droop). Set the external Mode Switch to "DROOP".
Bring the unit on the line.
Return the RATED SPEED or external Speed Trim potentiometer to the point marked in 2.
Now make adjustment to "DROOP" potentiometer in counterclockwise direction (decreasing Droop) until Full Load (Rated) is reached.Setting Droop For An Isolated Load
Run the engine and set the Mode Switch to the "DROOP" position.
With the load removed from the engine, set RATED SPEED or external Speed Trim potentiometer to the "No Load" speed. For example, for three percent droop, speed setting would be 61.8 Hz.
Apply 100 percent of the load to the engine.
With the engine fully loaded, make an adjustment to the "DROOP" potentiometer until either 50 or 60 Hz is reached.