Brushed DC motor - 4 pole field winding help

Thread Starter

amilton542

Joined Nov 13, 2010
497
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.
 

shortbus

Joined Sep 30, 2009
8,318
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.
 

Thread Starter

amilton542

Joined Nov 13, 2010
497
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.
 
Last edited:

shortbus

Joined Sep 30, 2009
8,318
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.
 

Thread Starter

amilton542

Joined Nov 13, 2010
497
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.
 
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