An exciter assembly for supplying a field current to the rotor windings of a superconducting synchronous machine includes a pulse transformer having a stationary primary winding, a secondary winding and a tertiary winding. A switched mode power supply supplies a pulsed voltage to the primary winding of the pulse transformer. The pulsed voltage developed at the secondary winding of the pulse transformer is supplied to the rotor windings through a pair of transfer leads. A controller controls synchronous rectification of the pulsed voltage supplied to the rotor windings based on a signal from the tertiary winding of the pulse transformer.