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Tutorial WIP How to drive AC motor: principles

Discussion in 'Motor actuators and drivers' started by RacingMat, Oct 21, 2015.

  1. RacingMat

    RacingMat Well-Known Member Gold Contributor

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    Hello!

    I'm wondering if I could go the AC route?... So I gathered some information that I'm sharing here:

    First, the posts from @speedy as a reference:
    Second, the principles:
    AC inverter principles.PNG
    Third, hardware to convert PWM signal to analog signal required by the inverter
    see the FAQ pwm-to-analog-signal-to-drive-vfd
    • Informative Informative x 1
  2. jem45472

    jem45472 Active Member

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    Just curious, why bother with ac? I never looked much into it, but it's probably really expensive to setup.
  3. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

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    One reason is to run really powerful motors.
    • Agree Agree x 2
  4. Pit

    Pit - - - - - - - - - - - - - - - - Gold Contributor

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    But meanwhile we can run powerful motors on the 12V/24V line as well. At least I dunno what is more expensive ;P
  5. RacingMat

    RacingMat Well-Known Member Gold Contributor

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    AC motors are mostly used in the industry. So the items are designed to be robust.
    Current intensity is smaller then you never fry controllers ;)

    Used AC motors can be a very good deal: 100$
  6. Pit

    Pit - - - - - - - - - - - - - - - - Gold Contributor

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    Which I have to complain - two of my 24V gear boxes are already damaged :( so if really big forces are needed AC could be cheaper at the end of the day...
    • Agree Agree x 1
  7. Historiker

    Historiker Dramamine Adict Gold Contributor

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    I too have been thinking about going AC, not for my 3DoF as it works fine with DC but for my 6DoF. After watching several videos of builds using Thanos' hardware and I am getting hooked. I know that I do not need Thanos' card as Speedy has shown a very good setup that we can use (as Mat mentioned). The cost, as far as I have worked out, would be triple what I have into my current setup but would give a better experience (only my opinion).
  8. cthiggin

    cthiggin Active Member

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    Hi folks,
    It took me over a year to source my 3 - 1hp Motors (MicroMax) and Boston Gearheads - 60:1, and they are built like a tank.
    My cost on these units were about 325.00 per Motor/Gearhead...............which is at least 1000.00 less per motor/gearhead if I bought them all new.

    PLEASE NOTE: Not any 3 phase motor will do............they MUST be INVERTER DUTY motors to be able to stand up to the constant forward/reverse functions required.
    An inverter duty motor is heavier built and has higher heat dissipation than ordinary motors.

    Tom
    • Informative Informative x 5
    • Like Like x 2
  9. Historiker

    Historiker Dramamine Adict Gold Contributor

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    I forget the name off the top of my head but the ones that I sourced are in use on several of the AC 6DoF setups that I have seen. I have found them on Ebay (motor and gearbox combo) for 100-200 or so. Course these are Chinese motors and not at all the quality of those that Cthiggin uses but they seem to do the trick.

    When I get home I will see if I can find them again.
    • Like Like x 1
  10. cthiggin

    cthiggin Active Member

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    Historiker,
    The Chinese units may be fine????
    I initially was going with SEW Eurodrive and had found 3 that would have worked, and would be about 500.00 US per motor/gearhead.
    I have a church friend that owns a very large motor repair business and he did some checking - and found that no one in the US serviced them and US could not get parts for them.

    I checked with several Chinese vendors, BUT, the shipping to US just killed those.

    I would imagine "IMHO" and your Chinese ones are with a helical gearhead attached, and in all probability are inverter-duty.
  11. Historiker

    Historiker Dramamine Adict Gold Contributor

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    SEW Eurodrive, that was the name, thanks Ctchiggin.

    As for who will service them, according to SEW Eurodrive USA these guys are the official service centers:

    Paducah Gear & Machine Co., LC5337 Gilbertsville Hwy.Calvert City, KY 42029270-395-0332270-395-0382
    Chalmer & Kubeck, Inc.150 Commerce Drive
    P O Box 2447Aston, PA 19014610-494-4300610-485-1484
    B&D Service525 12th StreetMacon, GA 31201478-742-8444478-741-1963
    C-B Gear & Machine, Inc4232 Mooney Road
    P O Box 111278Houston, TX 77293281-449-0777281-590-9127
    MarTech142 North Cluff AvenueLodi, CA 75240209-333-8478209-333-8479


    For local service both EMS Inc in nearby Grand Rapids and Electric Motor Service Center, also in Grand Rapids, tell me that they can get parts and service SEW Eurodrive motors. Of course I could never afford to have one serviced. If I could I would just buy new :)

    And true, new motors are expensive so I looked for a variety on Ebay such as this one (Exact same as used on a couple of successful 6DoF platforms). The hard part would be finding six matching motors/gearbox combos. I did find one vendor that had 8 available for 140.00 each. Shipping for most motors that I have found on Ebay range from 30-50 so I figured 200.00 per motor/gearbox.

    http://www.ebay.com/itm/SEW-EURODRI...hash=item3aa9768c6a:m:mt8DHpXCOJa5moZJKwdnGzQ
    • Winner Winner x 1
  12. cthiggin

    cthiggin Active Member

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    Historiker,
    At the time, I went with the info my motor guy told me, as he is a pro in "his" field.
    SEW Eurodrive are what most of the European Pros use for their platforms and other movement items.
    The particular one you linked too is a continuous drive...........motor is designed for constant, one direction movement......
    I couldn't tell what the torque was on the gearhead.....

    140.oo + shipping - 200.00 , well that's a super deal IF the motor/gearhead combination will meet your criteria in torque and inverter duty.

    Tom
  13. Historiker

    Historiker Dramamine Adict Gold Contributor

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    Good point Tom, that is a continuous duty motor on the gearhead. It is the same model number used on two 6DoF platforms on the other site. From what I read, continous duty motors are reversible with the addition of bleed off resistors (not sure I understand nor even have that right). If I did go this route I would of course have to learn a great deal more.
  14. cthiggin

    cthiggin Active Member

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    Historiker,
    From all I understand and have been told, all 3-phase motors are reversible.
    The catch - Continuous can be reversed.............but when we simmers are asking for a massive amounts of forward/reverse, it just beats the hell out of a continuous motor and the heat then becomes
    a real issue.
    - My manufacturer of my motors and VFD's state that you must use an inverter duty as well as many other threads that I have visited. It sure makes sense as my motors are very
    heavy and has a large fan on the rear to dissipate heat................must mean something.
  15. Historiker

    Historiker Dramamine Adict Gold Contributor

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    No argument from me Tom, you have a good set of motors. Always looking for new ways to do things though. I appreciate the information.
  16. cthiggin

    cthiggin Active Member

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    Historiker,
    IMHO, I would just hate to see you get 6 of something, and before long, would have to start replacing motors if using continuous.
    Of course, it would depend on amount of use etc...............maybe they would last a month or years.......such an open-ended situation with a bunch of variables.
    In retrospect, I feel blessed to have found mine...............identical motors / identical gearheads...........

    Blessings,

    Tom
  17. Historiker

    Historiker Dramamine Adict Gold Contributor

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    As you mentioned; depends on the use. They are designed for thousands of hours in an industrial setting. Several of the 6DoF AC rigs over "there" have been running successfully for a long time with simple motors. And from what I have read (and you mentioned) heat is the key enemy. They seem to be holding up very well. If the builder has enough money then by all means by the best you can get. Part of the fun of DiY is seeing what you can get away with ;)
  18. cthiggin

    cthiggin Active Member

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    Ditto...........I'm with you 100%....
    Again, I got very lucky on my finds and pricing......
  19. jem45472

    jem45472 Active Member

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    When I first started to research Sim building I was looking at ac. Went to work and looked at our motors and vfd's. Pricing at my work was $1000 per motor, $1000 per vfd's. Changes my mind quickly. I was unsure about scn5 reliability. The jrk's were a lifesaver for me. Now if I was going to do a flight Sim I think I would go ac for sure.
  20. cthiggin

    cthiggin Active Member

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    AC can be astronomical - all depends on what you are trying to accomplish.
    My "new" VFD's were 130.00 each..............but on the same site, I've seen the same brand, in other configurations, go at 1350.00 ea........
    In summary - AC is more expensive, but if configured correctly can be monetarily "doable"....an in my very humble opinion, will last for years.