Supplemental field excitation for permanent magnet rotor of pilot exciter

Claim 1

In a synchronous dynamoelectric machine having a rotor member disposed upon a shaft, said shaft being disposed for rotation by a prime mover, a field winding disposed on said rotor member, a main exciter having a stator member carrying a field winding and a rotor member disposed on said shaft carrying an armature winding, a rotatable rectifier assembly operable to convert alternating current to direct current having an input circuit connected to receive alternating current excitation from said main exciter armature and an output circuit connected to conduct direct current excitation through said synchronous dynamoelectric machine field winding, a pilot exciter operable to derive electrical power from the rotational energy of said shaft, said pilot exciter having a permanent magnet rotor member comprising a plurality of permanent magnets arranged in alternating magnetic polarity to establish a rotating magnetic field when said shaft is rotated, and said pilot exciter having a stator member carrying an armature winding which is coupled by magnetic induction with the magnetic field provided by said permanent magnet rotor member, the combination with said pilot exciter of a plurality of field coils disposed upon selected ones of said permanent magnets, said field coils being connected together in series electrical relation to constitute a field winding, and means for deriving direct current excitation from the output circuit of said rotating rectifier assembly connected to supply a predetermined function of said direct current excitation to said permanent magnet field winding.