Brushed DC motor - 4 pole field winding help

Discussion in 'The Projects Forum' started by amilton542, Mar 25, 2012.

  1. amilton542

    Thread Starter Active Member

    Nov 13, 2010
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    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.
     
  2. shortbus

    AAC Fanatic!

    Sep 30, 2009
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    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.
     
  3. amilton542

    Thread Starter Active Member

    Nov 13, 2010
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    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: Mar 25, 2012
  4. amilton542

    Thread Starter Active Member

    Nov 13, 2010
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    No worries, I've done it now. Problem solved
     
  5. shortbus

    AAC Fanatic!

    Sep 30, 2009
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    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.
     
  6. amilton542

    Thread Starter Active Member

    Nov 13, 2010
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    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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