Until now, I had no idea a 4-pole field winding arrangement could complicate brushed commutation.

As a frame of reference, the field windings consist of 4 poles, armature inherits saliency features by which again consist of 4 poles, and now I feel there is a need for another pair of brushes, 2 pairs in total, in order to eliminate any 'dead' coils.

Now, I'm not one to give in easily and after hours of internet research, thinking and drawing I finally fold.

What is the commutator arrangement to connect this up?

Any diagrams or links would be much appreciated, thanks.

 

If I understand what your saying, this is to run motor in reverse. It is done on "universal" motors, brushed motors that run on AC. Because the AC can't be reverse polarities like DC, to reverse rotate the motor, they use one set of field poles(180* apart) for one direction and the other set of poles (90* from the first set) for the other direction.

 

If I understand what your saying, this is to run motor in reverse. It is done on "universal" motors, brushed motors that run on AC. Because the AC can't be reverse polarities like DC, to reverse rotate the motor, they use one set of field poles(180* apart) for one direction and the other set of poles (90* from the first set) for the other direction.

From the YouTube video I've watched, this method is employed in starter-motors.

Please observe the video at 9:45.

http://www.youtube.com/watch?v=a_nsgzlrZGU

This is the same arrangement as the one I'm trying to build but with a 4-pole salient armature.

 

No worries, I've done it now. Problem solved

 

What was your solution?

I totally misunderstood you original question. I thought you meant you had a motor with four field poles and only two brushes.

 

What was your solution?

I totally misunderstood you original question. I thought you meant you had a motor with four field poles and only two brushes.

If you refer to the question carefully, I said , "I feel there is a need for another pair of brushes, 2 pairs in total, in order to eliminate any 'dead' coils."

This was the solution:

http://en.wikipedia.org/wiki/File:Modern_Consequent-Pole_Four-Field_Shunt-Wound_DC_Generator.jpg

I was just in need of a 'beautiful' diagram.