Requesting another device called a Saturable reactor. Is often a multi tap transformer. However has the ability to saturate the core with magnetic flux by means of an extra secondary or primary coil and providing DC current through it. The extra cool may have one leg attached to the other coils, much like a center tapped transformer. However the center tapped transformer in this program does not act like it should if used as a saturable reactor. The ability to do this allows the secondary to have variable AC voltage as you change the saturation in the core.