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  • High Speed (10,000 RPM) motor with variable speed drive

    Discussion in 'The main mechanical design forum' started by Barneel, Oct 16, 2013.

    1. Barneel

      Barneel Member

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      Now, this may well not be possible - in which case I'll have to come up with an alternative.

      BUT, if anyone has any neat ideas on how create a bad-boy like this (that is also preferably safe) you'll save me the price of a miniature turbine engine.

      What I need is a to find a motor capable of getting a (fairly hefty) 12" steel disc up to 10,000 RPM, as well as a variable speed drive capable of managing such a beast. Acceleration speeds and the like are no issues, the only requirement is that it can reach 10,000 RPM... and is safe (can contain it if necessary).

      It's for testing the accuracy of part of a device that measures the RPM of a turbine engine.

      Any helpful tips and pointers? I'm open to suggestions! Bodge-jobs are welcome (eg. one option I'm currently looking into is stripping down a disc sander).
       
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    3. JMarc

      JMarc New Member

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      They are many electric Synchronous motors developed for the Hybrid market capable of such speed. They are the best for this application as they have maximum torque at zero speed. But without any idea of acceleration rate required and moment of Inertia to drive to calculate torque and power the question is a bit too vague to answer. How and how deep are your pocket would be the next issue.
       
    4. musicalavtech

      musicalavtech Member

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      A few years ago, I worked in a factory rebuilding chip making machines. (80s & 90s technology) We installed motors to spin a 12" silicon wafer up to 10,000 RPM. The acceleration rate was extremely fast, and the accuracy of the speed was just about perfect.
       
    5. maniacal_engineer

      maniacal_engineer Well-Known Member

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      If you really don't care how long it takes to get to speed, then the power almost doesn't matter, nor does the size of the disc being spun, as long as you have really really good bearings. If you are going to use the speed of the disc rotating as a reference then the real issue is controlling the speed accurately. A synchronous motor driven by a variable frequency drive (VFD) would be a likely possible solution. if you try it with a regular induction motor it won't work because of slippage velocity.
       
    6. John OBrien

      John OBrien New Member

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      This might sound to simple however some grinders get up to 1200 rpm. I think a couple of pulleys should get you where you need to be. You will have to run another spindle to get there.
       
    7. johntargell

      johntargell Member

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      Hi you could use a Lynch motor - the speed is controlled by DC voltage but you would need a a gearbox to raise the speed from about 6,000rpm to 10,000rpm. the motor is small and very powerful (30N/m torque) so acceleration should be good but as others have said you will need very good bearings as this is a very high energy system and there's a lot of care required!

      Lynch Motors www.lmcltd.net

      Cheers John T
       
    8. T. Lewis

      T. Lewis New Member

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      Perhaps a brushless DC motor with electronic speed control. (common in the R/C hobby world) An example of a motor with sufficient power might be a 700-series from KDE Direct. That particular motor will run at ~12K rpm with the lowest rated voltage, but that can be driven lower. The challenge with this type of motor will be getting the speed down to the 10K rpm, but if you are willing to give up efficiency, just drop the voltage to the necessary level. The ESC (elect. speed control) can be programmed to any speed within a reasonable range. Gearing is always an options.
       
    9. ChrisW

      ChrisW Well-Known Member

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      Simplest way I can imagine is a router spindle. Depending on your requirements you can buy a Chinese product with VFD that will give you stable speeds in the range 9000-25000rpm.

      My cnc router has a 2.2kW head and with a VFD is a couple of hundred pounds from an EBAY trader. At the other end of the spectrum, a professional spindle of 10+kW will run to a few thousand but give you massive power. The speed is pretty stable when settled. Bearing capacity may be sufficient to support your flywheel if it's well balanced as the spindle has to support cutting forces.

      Big advantage is also the spindle has a collet chuck which you can use to adapt the drive.

      Take care with your containment, energy within the flywheel would send it a long way if it broke free!
       
    10. Barneel

      Barneel Member

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      Wow lots of replies! I would've come back to the thread sooner but I didn't realise I had any replies. I guess it must've cancelled the email notifications when my thread got moved.

      Thanks for all the responses, I've had a look into a few of them and the brushless motor mentioned by T.Lewis looks promising. I have contacted a couple of CNC spindle distributors but both told me this is something that should not be done if I value my limbs ;-)

      Efficiency isn't a major factor as the motor will be running for such a little amount of time it's not really worth considering. It's only purpose is to test the accuracy of a speed probe and the software that converts into an RPM at a range of speeds.

      ...I'll make sure this thing is perfectly rigid when I fix it down and contain it

      Thanks again for the replies!
       
    11. ChrisW

      ChrisW Well-Known Member

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      Barneel, whatever you use, unless you design from first principles you will have to do your own calculations and risk assessment.

      Router spindles are only certified for use as a router, the same for grinders or any high speed equipment (even hobby motors etc). Calculate the applied bearing loads then compare with the operation you propose.

      Finally, ensure full containment in the event of any failure mode, however you arrange the drive.
       

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