2-29. VOLTAGE REGULATORS
a. By far, the most commonly used and most efficient method of varying the
kilovoltage output of the high-tension transformer is the autotransformer control. If a
transformer is made consisting of one continuous winding on a long laminated iron core
and then voltage is applied across only one section of it, voltage will be induced in the
turns that are not connected directly to the line in the same way as voltage is induced in
the secondary of a conventional transformer. In fact, the section across which the line
voltage is applied is called the primary, and the balance of the winding is called the
b. If the voltage is measured across various sections of a typical
autotransformer, a situation like figure 2-18 might be present. By providing the
autotransformer with a series of taps or connections to the different turns, there would
be a convenient method present for getting a wide variety of voltages to apply to the
primary of the high-tension transformer. In the circuit shown in figure 2-18, the following
voltages could be obtained by setting the selector switch on the various taps: (This
circuit has a constant number of volts per turn).
Figure 2-18. Autotransformer with output selector.
Tap number 1--50 volts.
Tap number 2--100 volts
Tap number 3--150 volts
Tap number 4--200 volts