Armature Reaction & Brush Shifting

[QwertyXP]

Referring to a DC generator: one way to counter armature reaction is to shift the brushes. But I don't get how it works.

The direction of armature flux also changes when the brushes are shifted, so why does the MNA (magnetic neutral axis) not also rotate further.. If it does rotate further, then there would be no point in shifting the brushes!?

 

[meBigGuy]

does this explain it?

http://en.wikipedia.org/wiki/Armature_(electrical_engineering)

Shifting the brushes doesn't shift the neutral zone. just takes advantage of it (I think)

 

[FOIWATER]

That's correct. Changing the brushes into the neutral plane is the idea.

The neutral plane is the plane whereby no counteremf is induced in the winding under the brush.

The reason the MNA does not shift further is because it is a function of the main pole position, which does not shift with a brush shift