DC Series Generator

A DC series generator is self-excited DC machine in which the field winding is placed in series with armature conductors and hence the current in the field winding will be equal to the load current of the generator. As the series field winding carries the full load current they are made of relatively less number of turns and thick wires are used.

The terminal voltage for the DC series generator has rising characteristics and it increases with increase in load current. But at high loads the voltage
starts decreasing due to excessive demagnetising effects of armature reaction.

Usage of DC Series Generators

Series generators are rarely used in practice. They can be used as boosters for their rising voltage characteristics.

Circuit Diagram of DC Series generator

The given below figure shows the circuit diagram of a DC series generator.

Circuit Diagram of DC series Generator

Here E_g indicates the generated voltage in armature conductors and V is the terminal voltage of the series generator.

Equations for DC series Generator

If R_a is the internal resistance of the armature conductors and the R_se is the internal resistance of shunt field winding then the terminal voltage can be obtained as,

V=E_g-I_aR_a-I_seR_se

In DC series machine,
Armature current, I_a= Field current, I_se=Load current I_L

⇒ V= E_g-I_aR_a-I_aR_se

⇒ V= E_g-I_a(R_a+R_se)