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What are the advantages and disadvantages of n-pole motors?

  1. Jul 10, 2017 #1
    From what I've understand now, it is like in a brushed DC motor, the more poles you have, the less RPM but higher torque. Can anyone confirm?
  2. jcsd
  3. Jul 10, 2017 #2

    jim hardy

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    Have you tried an internet search ?
  4. Jul 11, 2017 #3
    Yes, I have. No helpful results so far.
  5. Jul 11, 2017 #4
    A great many AC and DC machines can be called "n-pole motors", where "n" is an even number of poles (2,4,6,8,etc).
    For an AC machine, synchronous speed (in RPM) is f*(2/p)*60, where f=AC line frequency, and p= the number of poles.
    i.e. for a 2 pole motor operated at 60 Hz line frequency, 60 Hz * (2/2) * 60 = 3600 RPM.

    Do a search on "motor poles" and read up.
  6. Jul 11, 2017 #5
    Did a search and all I got were about induction motors when I'm looking for the ones about brushed DC motors.

    Anyway. For brushed DC motors (given the same current), does more poles mean more torque and less RPM?
  7. Jul 11, 2017 #6

    jim hardy

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    Here's a pretty good introduction to DC motors


    While it's true that more poles gives more electrical degrees per mechanical degree of rotation
    it would be misleading to say that number of poles for a DC machine determines speed like it does in an AC machine.
    Should you accept it as a premise you'll wind up making mistakes in your thinking.

    Armature tangential velocity in a DC machine is ratio of applied voltage and field strength , neither of which depends on number of poles.
    Speed and torque will be more affected by motor's diameter and length than by how many poles it has.

    More poles means less armature slots per pole , so everything is inter-related
    but going down the line of thought you propose will cause confusion.

    Look up Lap vs Wave wound armature and you'll get into the tradeoffs designers use.
  8. Jul 12, 2017 #7
    Thank you for the good read, mate!
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