Saturable reactor

[1] This decreases inductive reactance and allows increased flow of the alternating current (AC).

Saturable reactors provide a very simple means to remotely and proportionally control the AC through a load such as an incandescent lamp; the AC current is roughly proportional to the direct current (DC) through the control winding.

In this way, the required magnitude of the control current can be kept roughly constant, no matter what the load.

Saturable reactors designed for mains (power-line) frequency are larger, heavier, and more expensive than electronic power controllers developed after the introduction of semiconductor electronic components, and have largely been replaced by thyristor dimmers using triacs or SCRs.

However, as of 2015, there has been renewed interest in using these devices for control of "smart grids" with multiple current tested installations in California, as well as the United Kingdom.

In concept, the alternating current through the lamp L can be controlled by the saturation of the iron core with the direct current, regulated by variable resistor R. B- battery, G – AC source.