Engine Tune-Up
after the speed stabilizes under no-load. If the speed
droop is correct, the engine speed will be approxi-
mately 3% to 5% higher than the full-load speed.
If the speed droop is too high, stop the engine, loosen
the droop adjusting screw and move the adjusting
bracket IN toward the center of the governor. Tighten
the screw. To increase the speed droop, move the
bracket OUT, away from the center of the governor.
The speed droop in governors which control engines
driving generators in parallel must be identical,
otherwise the electrical load will not be equally
divided.
Adjust the speed droop bracket in each governor to
obtain the desired variation between engine no-load
and full-load speeds. The recommended speed droop
for generator sets operating in parallel is 50 rpm (2-
1/2 cycles) for units operating at 1.000 and 1,200 rpm,
and 75 rpm (2-1/2 cycles) for units operating at 1,500
Fig. 10 - Adjusting Maximum No-Load Engine
and 1,800 rpm (Table 1). However, this speed droop
Speed
recommendation may be varied to suit the individual
5. Loosen the droop adjusting knob and move the
application.
slider all the way in toward the center of the governor.
Then tighten the knob.
EXTERNAL DROOP CONTROL
6 . Loosen the lock nut on the maximum speed
Some PSG type governors are equipped with an
adjusting screw (Fig. 10) and turn the screw out until
external adjustable d r o o p control (Fig. 9). This
5/8" of the threads are exposed.
p e r m i t s the speed droop to be adjusted without
removing the governor cover. With this feature, a unit
can be paralleled with another unit that is operating at
constant frequency (zero droop). The incoming unit
must have its droop bracket set in the maximum
p o s i t i o n while it is being paralleled and while
operating in parallel. When it is desired to stop the
unit operating at constant frequency, shift the load to
the incoming unit and move the governor droop
bracket to zero droop. Then adjust the outgoing unit to
maximum droop, remove it from the line and stop the
engine. The incoming unit will now be carrying the
load and operating at constant frequency (zero droop).
Adjust the governor speed droop as follows:
1. Start the engine and run it at approximately one-
half of the rated full-load speed until the lubricating
oil temperature stabilizes.
2. Remove the load from the engine.
3. Back off the compensation needle valve to release
any air that may he trapped in the system. Turn the
needle valve in slowly to reduce governor "hunting".
The correct needle valve setting will be between 1/8
and 1/2 turn open.
Fig. 11 - Typical Synchronizing Motor
4. Back out the minimum and maximum droop setting
Mounting
screws.
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