The load characteristics of series generator show the rising or booster characteristics and shunt generator shows the almost constant voltage with respect to load.
The combination of these two generators is known as compound generator. It has shunt wound and series wound.
Compound generators are classified into two dc machines.
- Long shunt compound generator
- short shunt compound generator
If the series field aids the shunt field then, it is called cumulative compound generator. If the series field opposes the shunt field then, it is called as differential compound generator. Accordingly, the internal wound connections.
Short shunt compound generator
By kvl , kcl
The equation of generated emf from circuit diagram,
Eg- Generated voltage
Vt- Terminal voltage
Ia- Armature current
Il- Load current
Ish - Shunt field current
ra, rse, rsh, armature ,series , shunt resistance. In this case, the armature reaction drop and brush drop is neglected.
Long shunt compound generator
by, kvl and kcl
The equation of generated emf from circuit diagram,
Load characteristics of dc compound generator
When the load increasing the load current in increases. The series field current is increases and flux is increasing and this series flux aids the shunt field flux there by generated emf is also increased. however, the terminal voltage is decreased in case of dc shunt generator.
The series field mmf are made such that the terminal voltage produces as same as rated voltage then, it is called as flat compound. The terminal voltage produces greater than rated voltage then, it is called over compound. The terminal voltage produces less than rated voltage then it is called as under
compound.
Applications of dc compound generator
This type of generator is used to maintain the constant voltage across the electrical appliances such as elevators, conveyers, air compressors and high torque load etc.
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