Hobart 6824-1 Operation And Maintenance Manual Download Page 80

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(1)

Adjust manual voltage control, variable resistor.

The adjustment of this resistor

(Ref. 1-1; 1, Fig. 7)

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 slider-band toward the single wire end of the resistor to increase voltage potential.

Move the band toward the double wire end (two wires connected) to decrease voltage
potential.

c. Tighten slider-band clamping screw.

(2)

Adjust 400-Hz voltage regulator.

NOTE:

The following adjustments are for the magnetic amplifier type voltage regulator,

identified by Hobart Part Number 430491C, illustrated herein, and covered by manual number
TM-759 in Chapter 6. For units having the newer solid state voltage regulator, refer to manual
number OM-2020 in Chapter 6.

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.

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).

OM-499

2-3