3-55
earlier in figure 3-34, a saturable-core reactor has an ideal operating point. Some d.c. must always be
applied to bring the saturable core to that operating point. This d.c. is called BIAS. the most effective way
to apply bias to the saturable core and also allow a.c. input signals to control the magnetic amplifier is to
use a bias winding. A full-wave magnetic amplifier with a bias winding is shown in figure 3-40.
Figure 3-40.—Full-wave magnetic amplifier with bias winding.
In the circuit shown in figure 3-40, the bias circuit is adjusted to set the saturable-core reactor at the
ideal operating point. Input signals, represented by the a.c. source symbol, are applied to the control input.
The true power of the load circuit is controlled by the control input signal (a.c.)
The block diagram symbol for a magnetic amplifier is shown in figure 3-41. The triangle is the
general symbol for an amplifier. The saturable-core reactor symbol in the center of the triangle identifies
the amplifier as a magnetic amplifier. Notice the input and output signals shown. The input signal is a
small-amplitude, low-power a.c. signal. The output signal is a pulsating d.c. with an amplitude that varies.
This variation is controlled by the input signal and represents a power gain of 1000.
