The DC machine comprises the construction of both Generator and Motor. The mode of working only decides whether DC generator or a DC motor. In this post, you will be getting to know “how dc machines work?” and also construction and working of DC machines.
Let us see the construction of DC machine in detail.
Yoke
The Yoke is the Outermost part of the machine which comprises of all other utilities.
The function of a Yoke
→ The main function of the yoke is to protect the machine dust, moisture and some of the gases like Sulphur dioxide and acidic fumes.
→ Yoke provides the mechanical support to the machine.
→ The yoke is a part of a magnetic circuit and it provides a low reluctance path for the magnetic flux. A low reluctance path is important to avoid the wastage of power to provide the same flux.
Choice of material
It should be of magnetic material in order to provide low reluctance path. The first preference would be of cast iron, for larger machines rolled steel, cast steel or silicon steel can be used.
Poles
Poles are divided into pole core and pole shoe.
Function of poles
The pole core contains a field winding which produces flux when energized.
Choice of material
It is made up of magnetic materials like cast iron or cast steel. The shape and size are more important for its operation.
Field Winding
The Field winding is wound on a pole core in a respective sequence.
The function of Field Winding
It helps in producing the magnetic field that is exciting the pole as an electromagnet. It is also called a field winding or exciting winding.
Choice of material
It carries current so metals (conducting) like aluminium or copper can be used. Copper can bend easily while compared to aluminium So the copper is preferred more.
Armature
The Armature is classified into armature core and armature winding.
Armature Core
The Armature core holds the cylindrical shape which is mounted on the shaft. It consists of slots and air ducts, which enhances the air flow and serves as a cooling purpose.
Functions of the Armature Core
→ The Armature Windings are wounded on the armature core.
→ It provides a path of low reluctance to the magnetic flux produced by the field winding.
Choice of material
It is usually made of magnetic materials like cast steel or cast iron to provide low reluctance flux. To minimize the eddy current loss, it is usually laminated.
Armature Winding
The Armatures windings mean the interconnection of Armature Conductors.
The function of Armature Winding
→ Emf is produced in armature winding, in case of a generator.
→ The current flow through the armature winding in case of motors.
→ To connect internal circuit with an external circuit.
Choice of material
The copper is used as an armature winding. The armature slot holds the conductor lined through an insulating material.
Commutator
The emf induced in the armature winding is alternating so for a DC generator, it should be rectified to get DC output, which is done by the commutator.
Function of Commutator
→ In case of a generator, to convert Alternating emf into unidirectional DC emf.
→ In case of motors, to provide unidirectional torque.
Choice of material
The commutator is also made up copper. It is cylindrical in shape. It consists of a commutator segment which is insulated from each other by a thin layer of mica.
Brushes
Function of Brushes
To connect internal circuit with the external circuit.
Choice of material
The brushes are usually made of soft materials like carbon.