Principle of Operation of Motoring

PRINCIPLE OF OPERATION OF MOTORING

The basic principle of operation of DC motor is that "whenever a current carrying conductor is placed in a magnetic field, it experiences a force tending to move it".

The magnetic field between two poles, N and S.

A current carrying conductor along the direction of the flux loops around it is:

If a current carrying conductor is placed between two magnetic poles, both the poles of fields will be distorted.

Above the conductor, the field is weakened and below the conductor the field is strengthened. Therefore the conductor tends to move upwards. The force exerted upwards depends upon the intensity of the main field flux and the magnitude of the current.

Then the direction of the current through the conductor is reversed. Here, the field below the conductor is less (weakened) and field above the conductor is more (strengthened). Then the conductor tends to move downwards.

The magnitude of the force experienced by the conductor in a motor is given by:

F = BIl newtons.

where, B = Magnetic field intensity in Wb/m².

I = Current in amperes.

l = Length of the conductor in metres.

The direction of motion given by Fleming Left Hand Rule, which states that if the thumb, fore finger and middle finger of the left and are held such that the fingers show three mutually perpendicular directions and if the fore finger indicates direction of the field, and the middle finger indicates the direction of current, then the thumb points the direction of motion of conductor.

In a DC motor, a strong electromagnetic field and a large number of current carrying conductors housed in an armature, make the armature rotate.