What is a dc motor, working and applications of dc motor

Hello guys how are you? Hope you are all good and well. 

Today we will discuss about, 

  • What is a DC motor. 
  • Types of DC motor
  • Construction of a DC motor
  • Working principle of DC motor
  • Working of DC motor
  • Applications of DC motor




What is a DC motor: -

A DC motor is an electrical machine which converts the electrical input power into the mechanical output power due to the interaction of magnetic fields. 

Types of DC motors: -

On the basis of the methods of excitation to DC motors, there are mainly two types of DC motors: -

1. Self excited DC motor
2. Series excite DC motor: - 

Series excited DC motor is further classified into three parts- 
  • Series excited DC motor
  • Shunt excited DC motor
  • Compound excited DC motor


Construction of DC motor: -

There is no difference in construction between the DC motor and DC generator. 

If the DC machine takes electrical power as input and gives mechanical power as Output, then it is called DC motor. 

And if mechanical power is input and electrical power is Output, then it is called DC generator. 

1. Yoke: -

The yoke is the outermost part of the DC machine. It may be made up of cast iron or fabricated steel. For small machines it is made up of cast iron and for large machines it is made up of fabricated steel to increase the permeability of the yoke. 

Permeability: - 
How easily the flux passes through the yoke is known as permeability. 
High permeability means less reluctance (opposition to magnetic field).

Main functions provided by the yoke: -
i) Provide a low reluctance path for the magnetic field. 
ii). It gives protection to the internal part of the machine. 

2. Poles: -

The pole is the place where field windings are accommodate. The poles spread out the magnetic field in the air gap between the field and armature winding. 

3. Armature: -

It is the most important part of the DC machine. It is the place where electrical energy is converted into the mechanical energy (in motor).
The armature windings accommodate into the armature slots and connected to the commutator. 
Note: -
The armature is made up of laminations to reduce the losses. 

4. Commutator: -

The commutator is that part of DC machine which connect the armature to the external circuit with the help of brushes. 

In DC generators, the commutators convert the alternating voltage into the unidirectional voltage. 
Whereas,
In DC motors, the commutators convert the alternating torque into the unidirectional torque.
It is made up of copper segments into a cylindrical shape. 
Commutators are insulated with the shaft, with the help of thin mica sheets. 

5. Brushes: -

The brushes connects the commutator with external circuit. 
It is made up of high grade carbon to provide low resistance. 

6. Bearing: -

As when the motor rotates, there are some friction losses into the motor which increase the losses into the machine. Therefore, to reduce the friction losses into the machine bearing is provided. 
It reduces the friction between the rotating part and stationary part of the motor.

7. Shaft: -

The shaft is the place from where we can take or give the mechanical power to the DC machine. 
In DC generators, mechanical power is given to the generator with the help of the shaft.
Whereas, 
In DC motors, mechanical power is taken from the motor with the help of the shaft.

DC motor working principle: -

It works on the principle that "whenever a current carrying conductor is placed in a magnetic field, a mechanical force will experience by itself." 

The direction of this mechanical force can be given by Fleming left hand rule. And the magnitude of this force will given by, 

F= Bil Newtons

Working of a DC motor:-

Let's understand it's working of a dc motor into some steps: -

1. There are mainly two windings into the motor, one of them is field winding and other is the armature winding. 

2. When a DC supply is given to the field winding, it will produce a static magnetic field which is known as main flux. 

3. The armature is placed between this flux and then DC supply is given to the armature with the help of the commutator. 

4. Due to this DC supply it will also produce a magnetic field which will interact with the main magnetic field and produce a force on the armature and thus armature starts rotating. 

5. When the armature of a DC motor rotates under the influence of this driving torque, the armature conductor move through the magnetic field and hence an emf will induce in it like a generator. 

6. This induced emf will act in the opposite direction (according to Lenz law) to the applied voltage and known as back emf or counter emf. 

* Back EMF is always less than the applied voltage. 

So applied voltage is given by,
Where,
V= applied voltage
E= back emf or counter emf
Ia= armature current
Ra= armature resistance 

Applications of DC motors: -

There are various applications of DC motors. Some of them given Below.

The DC motors are used in: -
  • Locomotives
  • Trolley 
  • Cranes 
  • Blowers 
  • Fans 
  • Elevators etc.

If you have any doubt then tell me in a comment. 

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Thank you.

Hope article helps you. 

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