The Alternator works on the principle of Electromagnetic induction. When there is a relative motion between the conductors and the flux, emf gets induced in the conductors. The dc generators also work on the same principle. The only difference in the practical alternator and a dc generator is that in an alternator the conductors are stationary and field is rotating. But for the understanding purpose, we can always consider the relative motion of conductors concerning the flux produced by the field winding.
Consider a relative motion of a single conductor under the magnetic field produced by two stationary poles. The magnetic axis of the two poles produced by field is vertical, shown by dotted lines.
Let the conductor starts rotating from Position 1. At this instant, the entire velocity component is parallel to the flux lines. Hence there is no cutting of flux lines by the conductor. So d∅/dt at this instant is zero and hence induced emf in the conductor is also zero.
As the conductor moves from position 1 towards position 2, the art of the velocity component becomes perpendicular to the flux lines and proportional to that, emf gets induced in the conductor. The magnitude of such an induced emf increases as the conductor moves from position 1 towards 2.
At position 2, the entire velocity component is perpendicular to the flux lines. Hence there exists maximum cutting of the flux lines. And at this instant, the induced emf in the conductor is at its maximum.
As the position of conductor changes from 2 towards 3, The velocity component perpendicular to the flux starts decreasing and hence induced emf magnitude also starts decreasing. At position 3, again the entire velocity component is parallel to the flux lines and hence at this instant induced emf in the conductor is zero.
As the conductor moves from position 3 towards 4, the velocity component perpendicular to the flux lines again starts increasing. But the direction of the velocity component now is opposite to the direction of velocity component existing during the movement of the conductor from position 1 to 2. Hence and induced emf in the conductor increases but in the opposite direction.
At position 4, it achieves maxima in the opposite direction, as the entire velocity component becomes perpendicular to the flux lines.
Again from position 4 to 1, induced emf decreases and finally at position 1, again becomes zero. This cycle continues as conductor rotates at a certain speed.
So if we plot the magnitudes of the induced emf against the time, we get an alternating nature of the induced emf as shown in the figure.
This is the working principle of an alternator.
Consider a relative motion of a single conductor under the magnetic field produced by two stationary poles. The magnetic axis of the two poles produced by field is vertical, shown by dotted lines.
Let the conductor starts rotating from Position 1. At this instant, the entire velocity component is parallel to the flux lines. Hence there is no cutting of flux lines by the conductor. So d∅/dt at this instant is zero and hence induced emf in the conductor is also zero.
As the conductor moves from position 1 towards position 2, the art of the velocity component becomes perpendicular to the flux lines and proportional to that, emf gets induced in the conductor. The magnitude of such an induced emf increases as the conductor moves from position 1 towards 2.
At position 2, the entire velocity component is perpendicular to the flux lines. Hence there exists maximum cutting of the flux lines. And at this instant, the induced emf in the conductor is at its maximum.
As the position of conductor changes from 2 towards 3, The velocity component perpendicular to the flux starts decreasing and hence induced emf magnitude also starts decreasing. At position 3, again the entire velocity component is parallel to the flux lines and hence at this instant induced emf in the conductor is zero.
As the conductor moves from position 3 towards 4, the velocity component perpendicular to the flux lines again starts increasing. But the direction of the velocity component now is opposite to the direction of velocity component existing during the movement of the conductor from position 1 to 2. Hence and induced emf in the conductor increases but in the opposite direction.
At position 4, it achieves maxima in the opposite direction, as the entire velocity component becomes perpendicular to the flux lines.
Again from position 4 to 1, induced emf decreases and finally at position 1, again becomes zero. This cycle continues as conductor rotates at a certain speed.
So if we plot the magnitudes of the induced emf against the time, we get an alternating nature of the induced emf as shown in the figure.
This is the working principle of an alternator.
I hope that this article will be informative for you all.
Thanks and Regards
Er. Abhishek Srivastava
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