Structure and Operating Performance of a Double Electrical Excitation Synchronous Generator With Embedded Brushless Synchronous Exciter Utilizing DC-Field Excitation

A double electrical excitation synchronous generator (DEESG) with an embedded brushless exciter is proposed to achieve brushless excitation for a brush excitation electrical excitation synchronous generator (EESG). A set of extra stator excitation windings is placed in the stator slots with armature coils to generate a static magnetic field. There are two sets of windings on the rotor: pulsating excitation winding (Wp) and main excitation winding (WF). The winding direction of the coils of Wpand WFon the same rotor-pole-body is the same. The AC voltage of Wpwhich is induced by static magnetic field provides dc excitation current for WFby diodes. Both currents in the coils of the Wpand WFgenerate the rotor excitation flux which induces voltage in the armature coils. In this study, the operating principle is analyzed theoretically. The no-load and load characteristics are studied using Maxwell. The influence of the novel winding structure on the output voltage when the load varies is also analyzed. The voltage regulation rate of DEESG is reduced because the rotor excitation currents can be increased with armature current. A 1.5 kVA prototype is fabricated for experiment. The measured results agree well with the theoretical and FE-predicted results.