Engine Tune-Up
droop is correct. the engine speed will be approxi-
Adjust Governor Speed Droop
mately 3% to 5% higher than the full-load speed.
INTERNAL DROOP ADJUSTMENT
If the speed droop is too high, stop the engine, loosen
The purpose of adjusting the speed droop is to
the droop adjusting screw and move the adjusting
establish a definite speed at no load with a given
bracket IN toward the center of the governor. Tighten
speed at rated full-load.
the screw. To increase the speed droop, move the
bracket OUT, away from the center of the governor.
The governor speed droop is set at the factory and
further adjustment should he unnecessary. However, if
The speed droop in governors which control engines
the governor has been overhauled, the speed droop
d r i v i n g generators in parallel must be identical,
must be readjusted.
otherwise the electrical load will not be equally
divided.
The best method of determining the engine speed is
by using an accurate hand tachometer.
Adjust the speed droop bracket in each governor to
obtain the desired variation between engine no-load
if a full rated load can be established on the unit, and
and full-load speeds. The recommended speed droop
the fuel rods, injector rack control levers and the load
for generator sets operating in parallel is 50 rpm (2-
limit have been adjusted, set the speed droop as
1/2 cycles) for units operating at 1,000 and 1,200 rpm.
follows:
and 75 rpm (2- 1/2 cycles) for units operating at 1,500
and 1,800 rpm (Table 1). However. this speed droop
1. Start the engine and run it at approximately one
recommendation may be varied to suit the individual
half the rated no load speed until the lubricating oil
application.
temperature stabilizes.
EXTERNAL DROOP CONTROL
NOTE: When the engine lubricating oil is cold.
t h e governor regulation m a y h e e r r a t i c .
Some PSG type governor are equipped with an
Regulation will become increasingly stable as
cxternal adjustment droop control (Fig. 10). This
the temperature of the oil increases.
p e r m i t s the speed droop to be adjusted without
removing the governor cover With this feature. a unit
2. Stop the engine and remove the governor cover.
can he parelleled with another unit that is operating at
constant frequency (zero droop) The incoming unit
3. Loosen the loch nut and back off the maximum
must have its droop bracket set in the maximum
speed adjusting screws approximately 5/8".
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
4. Loosen
the droop adjusting bolt on former unit+ or
unit operating at constant frequency, shift the load to
the screw
on current unit\ (Fig. 9). Move the droop
the incoming unit and move the governor droop
bracket so
that the screw is midway between the ends
bracket to zero droop Then adjust the outgoing unit to
of the slot
in the bracket. Tighten the screw.
maximum droop, remove it from the line and stop the
engine. The incoming unit will now he carrying the
5. With the throttle in the RUN position. adjust the
load and operating at constant frequency (zero droop).
engine speed until the engine is operating at 3% to 5%
above the recommended full-load speed.
Adjust the governor speed droop as follows:
6. Apply the full rated load on the engine and readjust
1. Start the engine and run it at approximately one
the engine speed to the correct full load speed.
half of the rated full load speed until the lubricating
oil temperature stabilizes.
7. Remove the rated load and note the engine speed
after the speed stabilizes under no load. If the speed
2. Remove the load from the engine.
No Load
Full Load
3. Bach off the compensation needle valve to release
any air that may be trapped in the system. Turn the
52.5 cycles. 1050 rpm
50 cycles, 1000 rpm
needle valve in slowly to reduce governor "hunting".
The correct needle valve setting will be between 1/8
62.5 cycles. 1250 rpm
60 cycles, 1200 rpm
and 1/2 turn open.
52.5 cycles, 1575 rpm
50 cycles, 1500 rpm
4. Bach out the minimum and maximum droop setting
62.5 cycles. 1875 rpm
60 cycles, 1800 rpm
screw\.
5. Loosen the droop adjusting knob (Fig. 10) and
TABLE 1
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