Do AC generators make use of interpoles?

[Jacob Anderson]

Hello, new member here. I'm giving myself a crash course and can't find a direct answer to my query outright, so here I am:

Do A.C. generators make use of interpoles? I understand the concept of interpoles in D.C. machines, offsetting neutral plane shift; however, if we have, say, a brushless ac generator that has an external prime mover and uses permanent magnets in lieu of excitation windings, are we even worried about neutral plane shift? If it's a 3-phase machine my gut says no, but again it's a self-inflicted crash course... Any help would be greatly appreciated!

 

[jim hardy]

Your intuition is correct. Without a commutator shift of magnetic field is of no consequence.

Armature reaction in alternators is what's behind their "Synchronous Impedance" .

old jim

 

[Jacob Anderson]

HUZZAH, thank you. That's been driving me crazy all day.

 

[Jacob Anderson]

Whilst we're here, is there any particular benefit of commutation over rectification?

Also, going with the pmac concept, would aligning all the poles in the same orientation have a negative effect other than reducing the available flux? Alas, at least for now, my final question: were one to arrange said magnets in halbach arrays, would they need to be aligned with the magnetic fields aligned axially or transaxially? That question is more for clarification, I'm leaning greatly towards transaxial so the coils cross the field lines more uniformly.

 

[salbay]

Whilst we're here, is there any particular benefit of commutation over rectification?

The only benefit for commutation would be if the brushes were on a rotating assembly , then you could change the output voltage and even direction by rotating the brush assembly, this would also change the emf constant and torque constant, so it would function like a variable gear ratio. Might be useful for a primitive diesel electric locomotive, where the primer mover was constant speed.?? I think the Ward Lenard set achieved this effect and dominated the variable DC motor control industry from 1900 on Ward Lenard Control