New Motor?

Discussion in 'General Science' started by BR-549, Apr 16, 2015.

  1. BR-549

    Thread Starter Well-Known Member

    Sep 22, 2013
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  2. alfacliff

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    Dec 13, 2013
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    so they are going to higher frequency ac motors? not a very new idea. we have motors here that put out 35 hp you can carry in one hand. just more poles and higher frequency.
     
  3. BR-549

    Thread Starter Well-Known Member

    Sep 22, 2013
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    They didn't give that many tech details.

    I believe the main idea was the power/weight.

    I think also they wanted to keep power/RPM slow for direct propeller and vehicle use.
     
  4. Glenn Holland

    Member

    Dec 26, 2014
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    I believe the world's record for power to size is about 2500 Hp in less than 1/2 cubic foot.

    It must have very high RPM and low torque and may have used super cooling in liquid nitrogen.
     
  5. alfacliff

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    Dec 13, 2013
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    we have motors here that are rated at 35 hp, that are easy to carry around. they run on 3 phase3 ac at up to 30,000 hz. also some motors I can carry in one hand rated at 10 hp. higher frequency motors are lighter in wate than lower frequency motors. thats why they use 400 hz on airplanes.
     
  6. strantor

    AAC Fanatic!

    Oct 3, 2010
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    I have spoken with Ed Dempsey of 400Hz engineering about building us an uncommonly tiny 200HP high frequency/high pole-count/low speed(<2000RPM)/high torque motor. He said that when increasing poles there comes a point where you start losing too much power. He said that above 10 poles, if the point is to cram the most power into the smallest space, it no longer makes any sense to continue increasing poles. Going that direction leads to a larger, heavier, more inefficient motor; better results can be achieved with a lower pole higher speed motor with a reducer gearbox (and fit in a smaller space, including the gearbox).

    So maybe you're right and they are using a high-pole-count high frequency motor, and Siemens has found a way around the inefficiency issue. Maybe with permanent magnets? But I suspect it may be a different approach to achieve those results.
     
  7. alfacliff

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    Dec 13, 2013
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    or a low pole count motor. a two p0ole 60 hz motor is rated at 3600 rpm (minus slip) and a 4 pole motor on 60 hz is rated 1800 rwpm (minus slip) why would you need more poles for higher rpm? using a good ferite mix for the poles would allow much higher frequency drive and rpm. the 35,000 rpm three phase spindle motor rated at 35 hp isnt very heavy, but it does require lisquid cooling, being inside the spindle assy. they use a Grasby - volksmann vfd to drive it, as part of a Henri Line milling center.
     
  8. MaxHeadRoom

    Expert

    Jul 18, 2013
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    The popular Chinese 3ph induction motor water cooled high rpm spindles reach around 24krpm, (400Hz VFD) but are limited to around 8000rpm min, due to their very low inductive reactance at any lower frequency.
    AC PM 3 ph servo's usually max out at 8 poles, the high pole count enables smoother control at lower rpm but the higher frequency required to obtain high rpm restricts them to around 6000rpm.
    Max.
    [​IMG]
     
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  9. alfacliff

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    The one we use can go real slow, even position. the drive goes much higher than 400 hz. even uses oil mist lube for the ceramic bearings.
     
  10. strantor

    AAC Fanatic!

    Oct 3, 2010
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    Not sure who you are addressing there; if it's me, I wasn't implying that you need more poles for higher RPM. I was talking about increasing frequency to reduce motor size, and in order to increase frequency while keeping RPM in a directly-usable (not requiring a reducing gearbox) range (<250oRPM per the atricle ) would require additional pole pairs.
     
  11. cmartinez

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    Jan 17, 2007
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    There's a very interesting video at the end of this article showing a NASA prototype with a 10-engine electric plane.
     
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  12. cmartinez

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    And btw, increasing the number of poles in a motor decreases its rpm, while it increases its torque and its efficiency too.
     
  13. strantor

    AAC Fanatic!

    Oct 3, 2010
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    These NASA guys get paid for this! I just decided: I want to work for NASA. I guess the first step would be to get my degree.
     
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