The DC motors and generators have same general construction.Hence a DC generator can run as a DC motor and vice versa .The essential parts are.
1.Magnetic frame or Yoke.
The outer frame or Yoke of DC machine provide for two functions.
a) It gave mechanical support to the poles and acts as a protecting cover for the machine.
b)It carries magnetic flux produced by the poles.
The Yoke is usually made up of solid cast steel.
2.Pole Core and Pole Shoes.
The field magnet consists of pole core and pole shoes.The field coils are supported on the pole core and pole shoe spread out the flux in the air gap.The large crossection of pole shoe reduce the reluctance of the magnetic path.
the pole core and pole shoes are made up of thin steel lamination.
3.Field Coils.
The field winding which consists of copper wire wound over the pole.When current is passes through this coils ,they electromagnetise the poles which produce the necessary flux that is cut by the revolving armature conductors.
4.Armature Core.
It houses the armature coil and cause them to rotate in the magnetic flux produced by the field system.The armature core is keyed to the machine shaft and rotate between the field poles.Armature core is cylindrical shaped and made up of circular steel laminations and each laminations are coated with thin insulating film.The purpose of lamination is to reduce Eddy current loss.
5.Armature winding.
The slots of the armature core holds insulated conductors that are connected in suitable manner.This is known as armature winding.In this winding working emf is induced.The armature winding of a DC machine is closed circuit winding.
6.Commutator.
A commutator is a mechanical rectifier that converts the alternating voltage generated in the armature winding into direct voltage across the brushes.Commutator is made up of Copper segments and insulated from each other by mica sheets and mounted in the shaft of the machine.The armature conductors are soldered to the commutator segments in suitable manner.
7.Brushes.
the brushes are used to ensure electrical connection between the rotating commutator and stationary external load circuits.The brushes are made up of Carbon and the rest on commutator.
