NOTE: The lower the percent of regulation, the better the generator. In the above example, the 5%
regulation represented a 22-volt change from no load to full load. A 1% change would represent a change
of 4.4 volts, which, of course, would be better.
Q20. What term applies to the voltage variation from no-load to full-load conditions and is expressed
as a percentage?
Voltage control is either (1) manual or (2) automatic. In most cases the process involves changing
the resistance of the field circuit. By changing the field circuit resistance, the field current is controlled.
Controlling the field current permits control of the output voltage. The major difference between the
various voltage control systems is merely the method by which the field circuit resistance and the current
VOLTAGE REGULATION should not be confused with VOLTAGE CONTROL. As described
previously, voltage regulation is an internal action occurring within the generator whenever the load
changes. Voltage control is an imposed action, usually through an external adjustment, for the purpose of
increasing or decreasing terminal voltage.
Manual Voltage Control
The hand-operated field rheostat, shown in figure 1-21, is a typical example of manual voltage
control. The field rheostat is connected in series with the shunt field circuit. This provides the simplest
method of controlling the terminal voltage of a dc generator.