Abstract: An exciter assembly for supplying power to a superconducting load, such as a superconducting field coil, disposed within a cryogenic region of a rotating machine. The exciter assembly provides an efficient and reliable approach for transferring the electrical power energy across a rotating interface and for controlling the ramp up and regulation of field excitation current in the field coil. In particular, the invention provides a controlled recirculation path for current flowing through the field coil. The exciter assembly includes a transformer having a primary winding and a secondary winding, a sensor which provides a control signal indicative of the flow of field excitation current to the superconducting load; and a current regulator which is disposed in the rotating reference frame and, on the basis of the control signal, regulates the field excitation current to a predetermined set.