Construction of DC Machine

The main parts of DC Machine (motor or generator) are as follows:

1. Yoke
2. Pole core and pole shoes
3. Pole coil and field coil
4. Armature core
5. Armature winding or conductor
6. Commutator
7. Brushes and bearings

Construction of DC Machine

1. Yoke

Yoke

• Function
  • It provide mechanical Support for poles
  • It also provide protection to whole machine from dust, moisture etc.
  • It also carries magnetic flux produced by the poles
  • Yoke is also called as frame.
• Material used
  • For small M/C yoke is made of cast iron.
  • For large M/C it is made of cast steel or rolled steel.

2. Pole & Pole core

Pole & Pole core

• Function
  • Pole of a generator is an electromagnet.
  • The field winding is winding over pale.
  • Pole provides magnetic flux when field winding is excited.
• Material used
  • Pole core or pole made of cast iron or cast steel.
  • It built of these laminations of annealed steel. The laminations is done to reduce the power lose due to eddy currents.

3. Pole Shoe

• Function
  • It is extended part of pole. It enlarge area of pole
  • Due to this enlarged area, flux is spread out in the air gap and more flux can pass through the air gap to armature.
• Material used
  • It is made of cast iron or cast steed.
  • It built of this lamination of annealed steel. the lamination is done to reduce power loss due to eddy currents

4. Pole coil or field windings

Pole coil or field windings

• Function
  • It is wound around pole core and called as field coil
  • it is connected in series to from field winding
  • When Current is passed through field winding it electro magnetize the poles which produce necessary flux.
• Material used
  • The material used for field conductor is copper.

5. Armature Core

Armature Core

• Function
  • It has large number of slots in its periphery
  • Armature conductor, are placed in this slots
  • It is also provide path of low reluctance to the flux produced by field winding
• Material used
  • High permeability low reluctance materials such as cast or iron are used for armature core.
  • The lamination is provided so as to reduce the loss due to eddy current.

6. Armature Winding

• Function
  • Armature conductor are inter connected to form armature Winding
  • When armature winding is rotated using prime mover. the magnetic flux and voltage gets induced in it
  • Armature winding is connected to external circuit
• Material used
  • It is made of conducting material such as coppers.

7. Commutator

Commutator

• Function
  • It Convert alternating current induce in the current in a unidirectional current
  • It collects the current form armature conductor and pass it load with the help of brushes
  • It also provide unidirectional torque for dc motor
• Material used
  • It is made of a large number of edge shaped segments of hard drawn copper.
  • The Segments are insulated from each other by thin layer of mica.
    OR
  • The Segment of commutator is made of copper and insulating material between segments is mica.

8. Brushes

• Function
  • Brushes collect the current from commutator and apply it to external load.
  • Brushes wear with time and it is should be inspected regularly.
• Material used
  • Brushes are made of carbon or graphite it is rectangular in shape.