Dc Motor

 

Dc motor converts Dc Electrical Energy into Mechanical energy. So it is said that the motor that runs on Dc power is called Dc motor. The two main parts of the  Dc motor  are field and armature. If the armature  circuit placed in the magnetic field generated  by the field pole is connected to an external electrical source,  a mechanical force will be produced in the armature conductor. As a result, the armature will start rotating.

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  Types of DC Motors:- The classification of DC motors mainly depends on how the field coil is connected to the armature. There are three types of DC motors namely:-

 1. Series motor 2. Shunt motor 3. Compound Motor.

Dc motor Construction:-

Dc motor Construction:-

  Starting method of DC motor:- 

 Only with the help of the main switch, the full line voltage is imposed on the armature while running the DC motor. Since there is no back EMF in the motor armature in the stable condition and at the same time the resistance of the armature is very low, when the full line voltage is applied to it, a large amount of current flows, thereby the possibility of burning the armature coils with the brush. Therefore, to keep the current of this starting time within a safe limit, resistance is attached to the armature and the work is done through the starter.

  As the motor starts moving slowly, the back EMF will increase and then the motor is brought back to its normal speed by reducing the value of the resistance.বাংলায় অনুবাদ করতে ক্লিক করুন.....

Dc motor starting technique

  Spread control method of a DC motor:- The speed of a motor will depend mainly on its work. In some tasks, the speed of the motor has to be changed continuously, while in some places the motor rotates only at certain speeds.  Somewhere again the machine has to be operated very slowly while doing fine types of work. So considering all these factors it is necessary to control the speed of the motor.

Field control method

  There are three methods of controlling the speed of the motor:- 1. Field control method, 2. Resistance control of the armature circuit, 3. The voltage control method imposed on the motor.

Resistance control of the armature circuit

Advantage of Dc motor:- 1. Dc motors are required  variable speed and high starting torque. 2. No Harmonic effect. 3. Low cost operation. 4. Needs low dc power for operate. 5. Good speed regulation.6. Simplicity, Availability.

Disadvantage of Dc motor:- 1. Short motor life. 2. Low efficiency. 3. Limited speed. 4. Mechanical noise.5. Brush to commutator arcing and wear. 6. Brush damage at a short time.

Use of Dc motor:- Toys and electronics watch, power vehicles, pull elevators and hoists, sewing machines, air compressors , mini microphones, etc.