Radar System Engineering

570 PRIME POWER SUPPLIES FOR RADAR [SEC. 14.5
compensation. The voltage is reduced either by a small auto-transformer
or by a dropping resistor.’ In any case, a variable resistor is
used, either on the a-c or d-c side of the rectifier, to provide a voltage
adjustment whose range is approximately 10 volts.
Figure 14.14 shows a carbon-pile regulator for use with a 10-kva,
3-phase, 208-volt engine-driven generator; Fig. 14.15 is a schematic
diagram of the circuit. Note the two potential transformers, connected
in open delta, which energize the regulating coil, so that the regulated
FIC, 14.14.—GeneralElectric Company voltage regulator for 10-kvaalternator
voltage is an average of the three line-to-line voltages. Note also the
antihunt circuit and coils on the solenoid.
It is probable that further development of the carbon-pile regulator
can greatly extend the usefulness of the device. At the close of World
War II, Leland Electric Company, of Dayton, Ohio, had developed
experimental models of improved carbon-pile regulators that appeared
to have a greatly extended operating range of resistance and improved
resistance to humidity as compared to earlier service models.
Finger-type Regulators.—Finger-type voltage regulators are similar
in operation to the carbon-pile type, except that the resistance is varied
in fixed steps rather than being continuously variable between minimum
and maximum resistance. Mechanical construction varies widely with
1A third method, employed on the 1500-va series PE-218 invert ers as well as a
number of others, is the use of a low-voltage tap on the armature wiading.