The series field of long shunt compound generator is excited by
Right Answer is:
Load current
SOLUTION
There art two types of compound generators:
- Short Shunt Compound Generator
- Long Shunt Compound Generator
Short-shunt compound generator in which only shunt field winding is connected in parallel with the armature, as shown in Fig. In short shunt connection series, the field carries no current at no-load and thus its open-circuit characteristics are the same as that of a shunt generator.
The series field of a short-shunt DC generator is excited by the series field current.
Where series field current is given as:
Ise = IL
Hence, the series field of a short-shunt DC generator is excited by the load current as shown in the figure of the short-shunt compound wound generator.
The current relations of the short-shunt connection of a d.c. compound generator is
la = If + IL
Where
Ia = Armature current
If = Field current
IL = Load current
Long-shunt compound generator in which the shunt field is connected in parallel will both the series winding and the armature, as shown in Fig. In long shunt connection, the series field winding carries the current same as that of shunt field winding at no-load. The series field of the long shunt compound generator is excited by Load-current.
The current relations of the long-shunt connection of a d.c. compound generator is
la = If + IL
Where
Ia = Armature current
If = Field current
IL = Load current
Two fields of the compound generators may be cumulative or differential wounds. If it is cumulative the two fields are additive and the two fields are subtractive if it is differential wound.
The essential difference between the two is that in the short-shunt connection, the armature current excites the series field, whereas, in the long-shunt connection, the load current excites the series field.