The motor which operates on a direct current (DC) supply is known as a DC motor. Direct current (DC) is the one-directional flow of electric charge. DC motor is a device that converts DC electrical energy to mechanical energy and then into rotational force. The input of the DC motor is electrical and the output is mechanical. The most common DC motors rely on the force produced by a magnetic field. Nearly all types of DC motors have some internal mechanism, either electromechanical or electronic; to periodically change the direction of current in a part of the motor.
Dc motor consists of the following
- Stator
- Armature
- Field winding
- Armature winding
- Commutator
- Brush
- Pole
- Yoke
- Pole shoe
- Bearing
- Core
- Shaft
Working principle
- We know that when a current-carrying conductor is placed inside a magnetic field it experiences mechanical force towards a particular direction. Let’s take a simple elementary model of DC motor in this model one single turn of the conductor is placed between two opposite poles that are north pole and south pole, as shown above, now if we start supplying DC through a commutator system to the single turn current starts flowing through it at that position as we see the positive terminal of the battery is connected with the left conductor and negative terminal of the battery is connected to the right conductor of the turn. The south pole of the magnet is placed at the left side and the north pole is placed on the right side current on the left side of the conductor flows inwards and the current of the right side flows outwards, as we see the conductor are carrying current and placed inside magnetic field both of then experience mechanical force acting on them the direction of the mechanical force can easily be determined by applying Fleming’s left-hand rule.
Fleming’s left-hand rule
- The direction of rotation of a DC motor is given by Fleming’s left-hand rule, which states that if the index finger, middle finger, and thumb of your left hand are extended mutually perpendicular to each other and if the index finger represents the direction of the magnetic field, middle finger indicates the direction of the current, then the thumb represents the direction in which force is experienced by the shaft of the DC motor.
- Due to these upwards and downwards forces the turn tends to rotate in the clockwise direction, hence we can say that whichever conductor comes under the south pole experiences an upwards and north pole experiences a downward mechanical force and due to these two forces the single turns continues to rotate until the battery is disconnected a practical DC motor rotates with the same principle. In DC motor in the place of a single turn, there is multi turns armature coil and in place of two poles, there may be more than two even numbers of poles.
Types of dc motors
- Permanent magnet dc motor
- Series dc motor
- Shunt dc motor
- Compound dc motor
