Principle of Operation for Generating

PRINCIPLE OF OPERATION FOR GENERATING

Let us consider a single turn coil ABCD rotated on a shaft within a uniform magnetic field of flux density. It is rotated in an anticlockwise direction.

Let 'l' be the length and 'b' be the breadth of the coil in metres. When the coil sides AB and CD are moving parallel to the magnetic field, the flux lines are not being cut and no emf is induced in the coil. At this position, we assume the angle of rotation 'θ' as zero.

This vertical position of the coil is the starting position. According to Faraday's law II, the emf induced is proportional to the rate of flux linkages.

where, "N" is the number of turns, "φ" is the flux and "t" is the time.

As N = 1,

Initially, when the coil is moving parallel to the flux lines, no flux line is cut and

hence,

During the first half revolution, current flows along ABLMCD through brush B₁ which is positive and into B₂ (negative brush). After half cycle AB and CD have exchanged positions along with the segments P and Q and current now flows, through DCLMBA. B₂ is now in contact with QCB, continues to be +ve.

For each half revolution, the position of position of segments P and Q also reverse. Hence the current in the load is always unidirectional. The change over the segments P and Q takes place when flux linkage (or) induced emf is minimum. In a generator, the split-rings are called commutator.