FIELD EXCITATION is the voltage applied to the main field windings. The current in the field
coils determines the strength and the direction of the magnetic field.
SEPARATELY EXCITED GENERATORS receive current for field coils from an outside source
such, as a battery or another dc generator.
SELF-EXCITED GENERATORS use their own output voltage to energize field coils.
SERIES-WOUND DC GENERATORS have field windings and armature windings connected in
series. Outputs vary directly with load currents. Series-wound generators have few practical applications.
SHUNT-WOUND DC GENERATORS have field windings and armature windings connected in
parallel (shunt). The output varies inversely with load current.
COMPOUND-WOUND DC GENERATORS have both series field windings and shunt field
windings. These generators combine the characteristics of series and shunt generators. The output voltage
remains relatively constant for all values of load current within the design of the generator. Compound
generators are used in many applications because of the relatively constant voltage.