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OM-2032 / Operation and Maintenance Manual
100D20 / Generator Sets
a. Adjust generator output voltage.
This is a relatively easy adjustment to make. With the generator running at a rated speed
(2000 RPM) and rated cycles-per-second (400 Hz), rotate the rheostat knob (1)
CLOCKWISE to INCREASE voltage and COUNTERCLOCKWISE to DECREASE voltage.
Observe the AC voltmeter and adjust output voltage to 115 V AC.
b. Adjust cable length and cable size compensation rheostats.
These two adjustment should be made together. Switch (4, Fig. 4) must be ON. Proceed as
follows:
• (aa) Adjust the rheostat (2) to point to the length, in feet, of output cable being used.
Various cable lengths are indicated on a plate mounted behind the rheostat knob.
• (bb) Adjust rheostat (3) to point to the size of cable being used. Various cable sizes are
also indicated on a plate behind the rheostat knob.
• (cc) With generator running (no load), check output voltage value, which should be exactly
115 V AC. If not, adjust in accordance with Para. 4, B, (2), (a) above.
• (dd) Apply a full load to the generator. Observe AC voltmeter. If the voltage observed
varies more than 1% (plus or minus) from 115 V AC, adjust rheostats (2) and (3) slightly to
obtain a voltage of 115 V AC, or as close to this value as possible. Turn knobs
CLOCKWISE to INCREASE voltage and COUNTERCLOCKWISE to DECREASE. Turn
each knob a small amount at a time to determine which rheostat is having the most effect
on output voltage and requires adjustment.
c. Adjust "damp" and "rate" adjusting potentiometers (see Figure 5).
Damping adjustments are very delicate and should not be attempted unless the generator
output average phase value varies more than 1 volt, or output voltage is unstable. "Damp"
and "rate" adjustments must be made in conjunction with each other because the adjustment
of one may affect the other. For example, improving the response by adjusting the "damp"
potentiometer (1) may affect the stability as adjusted by the "rate" potentiometer (2). Adjust
as follows:
• (aa) If "damp" and "rate" adjustments have been disturbed (changed from factory setting),
or if the regulator has been repaired, loosen locking nuts and set both potentiometers to
mid-position (halfway between full CLOCKWISE and full COUNTERCLOCKWISE).
• (bb) Connect the generator output to a balanced, three-phase load of 30 kilowatts.
• (cc) With generator running at 115 V AC no load, operate the contactor "on-off" switch (20,
Fig. 2). If the average phase voltage changed more than 1. volt, or if output is unsteady,
adjust "damp" and "rate".
• (dd) Turn the "damp" (1, Fig. 5) adjusting screw CLOCKWISE to improve response. Turn
COUNTERCLOCKWISE to improve STABILITY. Generally the best adjustment is
approximately 3/4 of full CLOCKWISE travel.
• (ee) Turn the "rate" (2) adjusting screw to near full COUNTERCLOCKWISE position. Turn
the screw slowly CLOCKWISE until the voltage output abruptly becomes STEADY.
Continue turning the screw CLOCKWISE 5 deg to 10 deg past this point for best "rate"
adjustment.
• (ff) Tighten adjusting screw locknuts after adjustment is completed.
Chapter 2-3
Page 12
March 31/94 Revised
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