Why DC excitation is used for alternators? Why cant it be AC?

Answer Posted / rvg.msceb

The basic requirement of an alternator is considered to be
as a sine wave generator. for getting pure sine wave, the
excitation to be of DC with low ripple factor.
in commercial generators, pure sine wave cannot be achived,
because of the core property of the material.

The excitation can of AC too. If we provide ac excitation,
the armature reaction will be more, and there by more core
loss, leads to heating up of core materials.The harmonics
disturbance also having consider effect in the power loss.

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