Why dc voltage used to excite alternator field in stead of ac?
Answer Posted / kj
When a wire is moved through a magnetic field it produces a
voltage across the wire. To produce an ac output the wire
must move past a north pole and then a south pole in
continuing sequence.
A dc voltage on the field will maintain the poles with the
same polarity. An ac voltage will cause the polarity to
reverse 100 times a second (50Hz) and this will not be
usable for generating the ac output voltage.
Usually an ac voltage is used but it is rectified either as
half wave or full wave before being put into the field.
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