Types of DC Generator

Types of DC Generator Points : Types of DC Generator, Machine With Respect to Methods of Excitation 2ndHeading D.C. machine can work as an energy converter only when its field winding is excited with direct current.
There are in general two ways of exciting the field: 1. Separately excitation The d.c. machine is called as separately excited machine. 2. Self excitation The machine is called as self excited machine.
1. Separately Excitation: In this case field winding is connected to an external d.c. source, and voltage of external D.C. source has no relation with the armature voltage. The field winding can be designed for nay convenient voltage. 2. Self Excitation When the field winding is energized from its own armature, the machine Is called as self excited machine, field poles must have some residual magnetism. When the armature rotates, it cuts the residual flux; small voltage (called residual voltage) appears across the brushes. This voltage establishes a current in field winding.
Self excited d.c. machine can be sub-divided as follows:
(a) Series excited d.c. machines.
(b) Shunt excited d.c. machine.
(c) Compound excited d.c. machine.