DC MOTORS-BASIC CONSTRUCTION AND WORKING
The machine which converts electrical energy into mechanical energy is called motor. The motor which operates on dc voltage is called DC motor. Dc motors are used for special purposes like steel mills, electric trains. In this topic we will study all about dc motor.
In dc motor armature generates magnetic field due to induction current. This magnetic field tends to rotate the armature in its direction of rotation, this effect is called electromagnetic drag. The drag provides mechanical energy in the form of armature rotation in dc motor. The DC motors works on the principle that when a current carrying conductor is placed in a magnetic field tends to move at right angle to the field.
A current carrying conductor is surrounded by a magnetic field. Since the conductor is paced between two magnetic poles and the direction of uniform magnetic field and that of the conductor field are at the right angle to each other therefore the lines of force remains under continuous tension.
Dc motors consists of following parts:-
- BRUSHES OF DC MOTOR
- FIELD WINDING
- ARMATURE WINDING
When a current carrying conductor is placed in the magnetic field. It tends to rotate at the right angle to the field. In figure a two pole motor is shown under north and south pole. The current in the coil under north pole is inward while the coil under south pole is outward as shown in figure.
Force and rotational torque act on both side of the coil which will tend to rotate the coil in the anti-clockwise direction as given by Fleming’s left hand rule. this force will act till the conductor is in the magnetic field. The motion however is not smooth and to make the motor run smoothly the single coil is replaced by several coils set at equal inclination to each other.
When a coil starts rotating after a very short time the side of the coil B will come under the north pole and side A under the south pole. In this way the current in the coil B side is inward while in the coil side a is outward it is automatically changed with the help of commutator.
In this way again in anti clock-wise force known as magnetic drag will act on the coil and coil will rotate continuously in a definite direction.
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