A new technique in obtaining self excitation for a brushless exciter by embedding permanent magnets on exciter poles.

摘要

Accordingly there is provided a brushless exciter capable of providing initial excitation power during field flushing enabling black start operation of brushless synchronous generators comprising a plurality of stator poles having pole surface; atleast one d.c. field winding for excitation; a three phase armature winding covering the rotor. A trapezoidal groove is configured on the pole surfaces in which a plurality of trapezoidal shaped permanent magnets being fixedly disposed. The magnets disposed north and south locations on alternate stator poles produce a magnetic flux h the air gap on providing a d.c field winding which causes the armature winding to generate sufficient voltage to provide the initial excitation power to the exciter. The proposed brush less exciter with self excitation has field coils as stator winding and three-phase armature winding. When a d.c supply is given to this stator winding, a magnetic field is set up in the air-gap. The rotor has three phase armature winding. The embedded magnets produces flux, which passes through the rotor and armature winding without any d.c supply being given to the stator winding/field coils. The Initial excitation power is obtained from the flux produced by embedded magnet. The developed brush less exciter has also been loaded to check the demagnetisation effect of the armature current. The exciter field winding is excited with d.c field current and it has resulted in increased output (excitation power for the generator). The reversal of filed current has reduced the initial excitation obtained by the embedded magnet and zero excitation level can also be achieved to obtain smooth control.