Principle and Working of DC Motor

In the simple form, let's discuss the Principle an Working of DC Motor in this post. Theoretically, the same DC machine can be used as a motor or generator. Therefore, construction of a DC motor is same as that of a DC generator.

Working Principle of a DC Motor

Working Principle of a DC Motor is: "Whenever a current carrying conductor is placed in a magnetic field, it experiences a mechanical force". The direction of this force is given by Fleming's left-hand rule and its magnitude is given by F = BIL. Where, B = magnetic flux density, I = current and L = length of the conductor within the magnetic field.

When armature windings are connected to a DC supply, an electric current sets up in the winding. Magnetic field may be provided by field winding (electromagnetism) or by using permanent magnets. In this case, current carrying armature conductors experience a force due to the magnetic field, according to the principle stated above.

Commutator is made segmented to achieve unidirectional torque. Otherwise, the direction of force would have reversed every time when the direction of movement of conductor is reversed in the magnetic field. This is how a DC motor works.

Type of DC Motor

DC motors are as follows,

1. Separately excited (field winding is fed by external source).
2. Self-excited.
1. Series wound (field winding is connected in series with the armature).
2. Shunt wound (field winding is connected in parallel with the armature).
3. Compound wound.

1. Long shunt.
2. Short shunt.