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OM-2032 / Operation and Maintenance Manual
100D20 / Generator Sets
are functioning properly. If load contactor is not opened within the above frequency range,
refer to Troubleshooting Chart to determine which component is defective.
(42) If the generator is operating under load at this point, place the contactor control switch (29, Fig.
1) in OFF position to open load contactor and disconnect load. There will be no further need
for the load bank in the following checks.
(43) With the engine running at normal governor speed; check the entire unit for vibration and parts
which may have become loosened during the above checks. Tighten any loose attaching
hardware as required.
WARNING
(44) Check 400-Hz generator bearings. Use a stethoscope or metal sounding rod to listen for
unusual noises. If using a metal rod, place one end on the generator housing and hold the
other end near the ear. Hold the rod with three fingers and use the index finger and thumb to
form a "sounding chamber" between the rod and the ear. Do NOT allow the rod to touch the
ear. Listen for "grinding" or pounding sounds which would indicate a defective bearing. An
engine noise may be "telegraphed" to the generator and misinterpreted as a generator noise. If
in doubt of bearing service ability, send unit to be overhauled.
3. Generator Set Adjustment
a. Generator Adjustment
The 400 Hz generator is a brushless type requiring no adjustments of any kind.
b. Generator Control Adjustments
The following items may require adjustment at some time during life of the equipment.
(1) Adjust manual voltage control, variable resistor.
The adjustment of this resistor (Ref. 1-1; 1, Fig. 8) determines the maximum generator output
voltage obtainable when using the manual control rheostat for voltage control. To adjust
maximum voltage potential, proceed as follows:
a. Loosen slider-band clamping screw.
b. Move the slide-band toward the single wire end of the resistor to increase voltage potential.
Move the band towards the double wire end (two wires connec ted) to decrease voltage
potential.
c. Tighten slider-band clamping screw.
(2) Adjust 400-Hz voltage regulator
NOTE: The following adjustment instructions are for the Hobart magnetic amplifier voltage
regulator, Part No. 430391C. For adjustment instructions for those generator sets employing
solid-state regulator Part No. 489812, and the solid-state regulator with current limiting, Part
No. 180822, refer to manual OM-2020 in Chapter 6 of this manual.
When a voltage regulator is first put into service, or when output (generator-to-aircraft) cables
are changed, the regulator may require up to five separate adjustments. The five adjustments
are for generator output voltage value, damping gain, damping rate, line drop compensation
gain and line drop compensation rate. See Figure 4 for identification of components used for
regulator adjustment.
March 31/94 Revised
Electric shock, moving parts, and noise can kill or injure! If a metal sounding
rod is used to detect bearing noises, exercise extreme care to avoid injury.
Chapter 2-3
Page 11
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