Abstract: Apparatus for controlling power transfer in an electrical induction device uses a controlled reactance to regulate the power transferred from an alternating current power source to a load without distorting or degrading the transferred power waveshape. The apparatus includes a power transformer having a power core and a primary coil and a secondary coil each encircling the power core. A number of control cores, separate from the power core, have associated control coils which are selectively short-circuited to provide the controlled reactance. The primary coil is arranged to encircle the control cores and coils and the secondary coil so that the primary coil is subject to the controlled reactance of the control cores.