DC MACHINES
Dc machines are electromechanical energy converters there are two types of DC machines the DC generator and DC motor each Dc machines can act as a generator and a motor. It usually works from a DC source and generates mechanical power or it will convert mechanical power into Dc power.
A Dc generator converts mechanical power to DC electrical power
DC motor converts electrical to mechanical
There are mainly two parts for Dc machines a stator and a rotor both of them are separated from an air gap the stator is situated outside of the machine and it cannot move and the rotor is different from the stator it is situated inside the machine and it can move both of them are made up of ferromagnetic materials
The conductor is placed in the inner slot of the stator and in the rotor conductor is placed in the outer slot and these are interconnected and thus it would be a winding
Armature winding is the one in which voltage is induced and field winding is the one in which the current is passed to produce main flux
CLASSIFICATION OF DC MACHINES
DC machines are classified according to their magnetic structure
They are HOMOPOLAR MACHINES, HETROPOLAR MACHINES
HOMOPOLAR MACHINES
Homopolar generators
The conductors are placed in such a form that they always move in one polarity either north or south pole. The conductor conducts magnetic flux on the same polarity and thus it is called a homopolar generator either it has an electrically conductive disc or a cylinder which will be perpendicular to the magnetic field there will be a potential between the center of the disc and the rim with an electrical polarity which will be depended on the direction of rotation and orientation of the field
HETROPOLAR DC GENERATORS
In this case, induced emf of the conductor goes through a cycle change in voltage when it passes through the north pole and south pole alternately and thus the induced emf of the conductor is not constant it varies in magnitude. The induced emf is directly proportional to the flux density for a constant velocity of a sweep if the density of the flux variation is sinusoidal in space then a sine wave voltage will be created we must add a commutator with the winding if we need to get a steady DC voltage
