Radar System Engineering

SEC. 14.5] VOLTAGE REGULATORAS 567
theothe rendisretaine dbyascre wusuallyreferred to as the pile screw
or pile-adjusting screw.
The control element of the regulator is a solenoid coil and armature.
The current through the solenoid coil is proportional to the voltage to
be regulated, andthe pull of itscore onthearmature is proportionalto
the air gap between the two, and
to the coil current. The air gap
is adjustable by movement of
120
thecore; this constitutes one of the ~
adjustments to be made on the & :
regulator. ~ 115
With the core in fixed position ~
and the pile-adjusting screw tight, ~
the output voltage of the generator
will be high. As the pile screw is 110 - out Inloosened
the voltage will drop, reach
Pile. screwturns
a minimum point, rise, and then
FI~. 14.10,—Carbon-Pileregulatoraddrop
again as shown in Fig. 14.10. volts. Point B—optimum operating point
j ustment. Point A—bottom of dip—115
The generator will regulate properly ‘117 ‘“lts.
to the left of the hump or to the right of the dip. Between these two
points, that is, on the downward slope of the curve, regulation will be
unstable. The slope of the curve to the left of the peak is less than
that to the right of the valley, giving better regulation. However, in
this region the carbon pile is under less pressure, and is thus more suscepti-
FI~. 14.1 1.—Output waveform showing amplitude modulation.
ble to mechanical vibration and shock. Most recent practice, therefore,
is to adjust the regulator to operate on the right-hand side of the dip.
When carbon-pile regulators were first used on inverters they were
mounted directly on the rotating machine. This gave rise to serious
troubles because of the susceptibility of the regulator to vibration.
Vibration of the carbon pile causes amplitude modulation or “jitter” of