Construction Of DC Machine (English)

In this post we will all study Construction Of DC Machine instead of Construction Of DC generator which will be same for both DC generator and DC motor, as both DC generator and DC motor have same structure. When these machines are manufactured the employees do not know whether it is a DC motor or a DC generator. Hence any DC generator can be used like a motor without any change in its structure and DC motor can be used as a DC generator.

The structure of DC machine is mainly divided into two parts.

1.) Stationary Parts: -

2.) Rotating Parts: -

(1) Stationary Parts: -

The parts of the DC machine that remain stable even when the machine is running. This part of the machine is called the magnetic field system, which acts as the generator of the magnetic field and conductor of these magnetic fields. The following parts come under the magnetic field system. We will study all those parts in detail below.

Yoke

The outer hollow cylindrical cover of the DC machine is called a yoke, which completely covers the entire machine. The poles and inter-poles are installed on the yoke itself.

The yoke of a small size DC machine is made of cast iron, while in larger machines it is made of cast steel or rolled steel.

Following are the main functions of the yoke: -

1. It acts as a mechanical base as it provides the basis for some parts of DC machine like poles and inter-poles etc.
2. The yoke provides mechanical protection to the machine from dust, moisture and external injury.
3. It acts as a good carrier for the magnetic fields generated in the machine.

Pole & Pole core-

• In a DC machine, Pole is used to generate the main magnetic field.
• It is installed by welding on the yoke of the DC machine or with the help of a bolt.
• A pole is an electromagnet that is binding to produce a main magnetic field.
• To excite the electromagnet of the DC machine ie Pole is supplied from any external DC source such as battery etc., which causes the Pole to generate magnetic field.
• Pole is made of thin lamination's of silicon steel.
• To make the pole, use thinner lamination's to reduce the power loss caused by eddy currents.

Pole shoes-

The surface in front of the pole of a DC machine is slightly bent, which is called the pole shoes.

• The area of ​​its cross section is more than the area of ​​pole.
• The main function of the pole pole is to keep the binding on the pole in its place and to evenly propagate the magnetic field generated by the pole on the armature.

Field winding-

The winding done at the pole of a DC machine to generate the main magnetic field is called field winding.

• When the field winding If an electric current is passed through an external DC source, it produces a magnetic field.
• The field winding of each poles are connected to each other in series in such a way that when supplied to them, their poles are sequentially forming the North Pole and South Pole.
• Commonly used copper conductors to do field winding on the pole.

(2) Rotating Parts: -

This is the part of the DC machine that starts rotating when the machine is powered on.

Armature-

An armature is the part of a DC machine that rotates in the magnetic fields generated by the machine's pole.

• It is cylindrical and is installed on the shaft of the machine.
•  It is made by laminating circular discs of silicon steel.
•  A lot of grooves are made on its periphery in which armature winding are installed.
•  It has some air vents for cooling purposes.

Armature winding-

Armature winding is a place where mechanical energy is converted into electrical energy.

• It is installed in the grooves on the perimeter of the winding armature.
• The conductor used for this winding is normally copper.
• When the armature is rotated in a magnetic field by a primary conductor, the emf is induced in the armature winding.

Winding on armature is done in the following two ways-

1. Lap winding
2. Wave winding

Commutator-

In a DC generator, the commutator converts the induced alternating current into a unidirectional current through the brush, 

While the DC motor converts the commutator alternating force moment into a directional force moment. It is because of this property of commutator that it is called mechanical rectifier.

• It is cylindrical and rotates along the armature.
• The commutator is made of segments. These segments are insulated from each other by a layer of mica.
• The number of these segments is equal to the number of armature coils and an armature coil is attached to each segment through riser.

 Brush-

The brush armature provides the external circuit by storing the electric current from the winding or the current from the external circuit
You Can Also Like  This Post -
Principal OF DC Motor
Working Of DC Motor (English)