Self Excited DC Generator

Self Excited DC Generator

Self-excited DC Generator is a device, in which the current to the field winding is supplied by the generator itself. In self-excited DC generator, the field coils mat be connected in parallel with the armature in the series, or it may be connected partly in series and partly in parallel with the armature windings.

The self-excited DC Generator is further classified as

Shunt Wound Generator

In a shunt wound generator, the field winding is connected across the armature winding forming a parallel or shunt circuit. Therefore, full terminal voltage is applied across it. A very small field current Ish, flows through it because this winding has many turns of fine wire having very high resistance Rsh of the order of 100 ohms.

The connection diagram of shunt wound generator is shown below.

Shunt Wound DC Generator

Shunt field current is given as

Where Rsh is the shunt field winding resistance.

The current field Ish is practically constant at all loads. Therefore, the DC shunt machine is considered to be a constant flux machine.

Armature current is given as

Terminal voltage is given by the equation shown below.

If the brush contact drop is included, the equation of the terminal voltage becomes