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Thread: Axial vs. Radial air gap motors

              
   
   
  1. #11
    Moderator Nuts & Volts's Avatar
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    I agree with magicsmoke. It all has to do with mechanical failure of the materials in the motor. Too much voltage will cause the motor to overspeed, which will tear the motor apart. Thats why sometimes you see people wrap a motor with kevlar so they can get more power (from more speed) out of a low voltage rated motor. The other issue that overvoltage can cause is arcing, but thats another topic.

    Kyle

  2. #12
    teddillard
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    I guess all I read from that is that if the motor overrevs and fails, it can blow apart since there's no shell of coils or magnets that you'd have with a radial motor... but it does bring up the interesting point that the axial motor has a larger diameter rotor compared to the case than an radial, theoretically giving you more torque- again, since the thickness of the magnets isn't there.

    I'm not sure I'm following the logic here... it seems pretty much a slam-dunk that the axial armature has a lot more potential stress than the radial.

  3. #13
    Senior Member chdfarl's Avatar
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    Its funny that you restarted a thread from the old site without realizing it. I posted the same subject but no one commented. The issues that I saw wasn't the motor breaking up. Its common physics that if a round object is spun it is easier to push the outside edge rather then the sides. So why are axial gap motors so popular. Wouldn't the radial gap use less torque ( amps ) and wouldn't it spin faster since the reduced profile. id love to test that theory but motors are expensive.
    There's my two bits don't spend it all in one place.

  4. #14
    teddillard
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    Well, I think the performance stats are pretty much out there and speak for themselves. For my part, my original post was just about figuring out what the heck the difference between the two configurations was.

    Next week: SEPEX!

    lol!

  5. #15
    Empulse R #24 frodus's Avatar
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    difference:

    one has motors that have their north/south poles pointing in the same direction as the shaft. i.e. magnets are on each side of the armature.

    The other has their north/south poles pointing towards the center of the shaft. i.e. magnets are on the outside of the motor, just like field windings.

  6. #16
    teddillard
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    so, maybe a dumb question, but that made me think- are axial gap motors ONLY permanent magnet?

  7. #17
    Senior Member chdfarl's Avatar
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    Specs are published by the companies that sell them and not to the extent id like. A real world beating and dyno testing not theoretical calculations. You know the value of real world independent testing thats why there are motorcycle magazine tests

  8. #18
    Senior Member larryrose11's Avatar
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    OK,
    For the radial gap motor, ALL of the car OEM traction drives have the coils on the outside, where it is much easier to liquid cool, helping the power density of the motor. You would have a difficult time liquid cooling a axial gap motor, limiting the power density.

  9. #19
    Senior Member chdfarl's Avatar
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    coils on the outside isn't that brushless DC like the AC but using perm magnets
    like the motor used on the Motoczysz e1pc
    Last edited by chdfarl; 18 August 2010 at 1752.

  10. #20
    Empulse R #24 frodus's Avatar
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    I should have clarified maybe....

    It can be coils OR a magnet. Its mostly used to describe how the fields oppose. Either axially (inline with the shaft), or radially outward (perpendicular with shaft).

    BLDC can be axial or radial as well, but with BLDC, the magnets are on the rotor.

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