Function of Each Part of D.C Generator
A D.C Generator consists of the following parts:
1. Yoke or magnetic frame
2. Pole cores and pole shoes
3. Field windings
4. Brushes and brush holders
5. End covers
6. Armature core
7. Armature winding
8. Commutator
9. Shaft
Fig 1. DC Generaotor Parts
1. Yoke or magnetic frame: The outer most frame is known as
Yoke. It is made of high permeability material possessing sufficient mechanical
strength. Cast iron is used in small machines and cast steel or rolled steel is
employed in large machines.
The
Yoke serves two fold as:
(a)
It
protects the entire machine from dust and dirt and also provides mechanical
support for the magnetic poles.
(b)
It
acts as the return path for the magnetic flux.
2. Pole cores and Pole shoes: the field magnet consists of pole
core and pole shoe. In modern design, the complete pole cores and pole shoes
are made of thin (about 0.5 mm thick) laminations of annealed steel which are
pressed together and riveted and are secured to the yoke by means of screws
bolted in to steel rod.
The main function of the pole core is to establish the
required magnetic flux. The field winding is placed on the pole core. When (field)
current passes through this field winding the core becomes an electromagnet and
establishes the magnetic flux. The flux can be varied by varying the current
through field winding.