Saturated Core Reactor acts as a variable inductance connected in series with load across an A.C power supply. Its look like a transformer having two or more windings around a core of steel. However one of these windings receives a small direct current (DC) which act as an I/P signal which controls the amount of A.C that can flow through A.C winding and load the O/P current and load voltages are increased as the D.C I/P is increased and vice-versa.
A Saturated Core Reactor can have a single core and only one A.C winding as shown in figure (A) this type of reactor is used since the alternating current in the upper winding producing an A.C voltages in the lower winding (D.C winding) that may be disturbed or damaged the DC control circuit. Therefore most of reactors included two AC coils (windings) as shown in figure (B). Each steel core has its own AC winding while the DC coil surrounded on one leg of the steel core. The two AC winding s are connected in parallel but the connection of the lower coil are reversed to that of upper AC coil. It is because when flux move to the left AC coil.
In the DC coil these fluxes are in opposite direction at the same time. Therefore both the flux canals each other and no voltage is induced in the DC coil.