Figure 3-34.Magnetization and permeability curves with operating point.
When the saturable-core reactor is set at the knee of the magnetization curve, any small increase in
control current will cause a large increase in load current. Any small decrease in control current will cause
a large decrease in load current. That is why point "O" is the ideal operating point-because small changes
in control current will cause large changes in load current. In other words, the saturable-core reactor can
amplify the control current. However, a saturable-core reactor is NOT a magnetic amplifier. You will find
out a little later how a magnetic amplifier differs from a saturable-core reactor. First you should know a
few more things about the saturable-core reactor.
If a d.c. voltage is applied to the control winding of a saturable-core reactor and an a.c. voltage is
applied to the load windings, the a.c. flux will aid the d.c. flux on one half cycle and oppose the d.c. flux
on the other half cycle. This is shown in figure 3-35. Load flux is indicated by the dashed-line arrows, and
control flux is indicated by the solid-line arrows. View (A) shows the load and control flux adding during
one half cycle of the a.c. View (B) of the figure shows the load and control flux opposing during the other
half cycle of the a.c.
Figure 3-35A.Flux paths in a saturable-core reactor. FLUX AIDING