types of alternators

[gjo]

In my book it says "a variation of the revolving armature AC generator is often used for very low power (e.g. , an automobile alternator) where both windings are interlaced on a stator and the fields are coupled by a rotating soft iron (electromagnetic) armature without windings."

I don't understand what they mean by "both windings". And why are they interlaced. Also how does the armature operate with no windings and what do they mean by " electromagnetic"?

 

[chuckey]

I would call this a variable reluctance alternator. Lets go from step 1, imagine a toothed cog with its teeth being very long and bent over so they all face along the shaft. If you wind sets of coils on alternate teeth,output coil, magnetising coil, output coil, magnetising coil. Now if the magnetising coils have current flowing through them, so they are little magnets and magnetic cog with teeth is spun on the shaft, as its teeth line up with the little magnets, their field will increase, which will induce a voltage in the output coils. I have never seen one used as a car alternator. They have the advantage that as all the coils are stationary, no brush gear or slip rings are required.
Frank