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Thread: How Do I Make My Own Variable Frequency Drive?

  1. #1
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    Arrow How Do I Make My Own Variable Frequency Drive?

    I don't know much about this stuff. I don't have a rotary phase converter, or a static one for that matter, but I want to buy a more powerful motor for my lathe. Of course, it is a 3 phase motor, and I was hoping to be able to go from a step pulley system to a variable speed drive. Anybody know how to do this for the least amount of money? Thanks.

    Hutch

  2. #2
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    Not sure that a VFD is a DIY project that I would tackle - but they can be found rather inexpensively for the smaller HP motors 10hp and less. By inexpensive I mean less than a new motor. But your motor should be rated for VFD use, the Pulse Width Modulated wave form is a bit harsher on the motors that are not designed for it.

    http://www.yaskawa.com/site/Products...%7EVSmini.html
    http://www.yaskawa.com/site/AdCampai...nt&promo=V1000

    Or just search "Variable Frequency Inverter drive" through Google or Dogpile and you will find quite a few. I just checked and there are several on Ebay for less than $100.
    Last edited by David Epperson; 04-11-2008 at 3:09 PM.
    The opinion of 10,000 men is of no value if none of them know anything about the subject.
    - Marcus Aurelius ---------------------------------------- -------------

  3. #3
    Yes, it can be a relatively easy modification and many of us have done it for older lathes. This is well written about, try some searches on this site.
    I changed an old Rockwell 12" gap bed to a 1.5 hp 3 phase motor and VFD drive to regulate the speed for about $250 about 18 months ago.
    Rich S.

  4. #4
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    Motor

    I have been looking into the VFDs, but I wasn't sure if I needed a special motor. Can I throw one on to any 3 phase motor? I know I need to pay attention to output amperage, but beyond that I need guidance. Is it this simple? I will continue my web searching. Thanks.

    Hutch

  5. #5
    It is really simple to do unless you make it complicated. A properly sized VFD will work on an old or new 3 phase motor. The inverter duty motors will have better performance but are not really necessary for a wood lathe. If you have a choice between two motors, get the slower one.

  6. #6
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    This is a easy project, the VFD must match the hp of the motor. They sell VFD's in many price ranges, more expensive units have a bunch of options that you don't need.

    Electrical is basic, bring 220 into the VFD (2 hots and a ground). The output is L1, L2 and L3 and ground, these need to be connected to the correct wires on the motor. Read the manual with the VFD and the tag on the motor.

    The hard part is to make a bracket to mount the VFD. I use sheetmetal to mount the VFD that is bent to a "L" shape (if you look from the side) if you bore two holes on the bottom of the "L" the wire cable can be held in place.

    Like Dennis said you don't need to spend a bunch of money on a wood lathe and it will be fine. I did a CNC lathe with some nice stuff and it was only $675

    If you need help just ask.
    Doug
    Last edited by Doug Thompson; 04-12-2008 at 3:31 AM.

  7. #7
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    Here's what I am looking at

    Well, I have my eye on an unused 4 HP, 3 ph, 1155 rpm motor. It's would cost about $275. However, I am not sure there is a VFD that can input single phase at this HP. I have only seen 3hp drives and lower with single phase input. Also, I haven't seen many 3 hp VFDs for less than $225. Do you guys have a specific source that's better than others? Thanks for all the info so far.

    Hutch

  8. #8
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    That's a lot of money for a 3PH motor. I paid $35 for a used 2HP, 3PH motor.

    If you stay at or under 3HP, this line of drives will work for you.
    http://www.factorymation.com/s.nl/sc.2/category.32/.f


  9. #9
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    Quote Originally Posted by Matt Hutchinson View Post
    Well, I have my eye on an unused 4 HP, 3 ph, 1155 rpm motor. It's would cost about $275. However, I am not sure there is a VFD that can input single phase at this HP. I have only seen 3hp drives and lower with single phase input. Also, I haven't seen many 3 hp VFDs for less than $225. Do you guys have a specific source that's better than others? Thanks for all the info so far.

    Hutch
    The Yaskawa V1000 drive specs say it will go to 5hp 17.5 output amps with a 240V single phase input. That's the CIMR-VU BA0018.

    I'm sure that it is not the only one.
    The opinion of 10,000 men is of no value if none of them know anything about the subject.
    - Marcus Aurelius ---------------------------------------- -------------

  10. #10
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    Service factor

    Ok, I changed my mind. After deliberating with a few sources, I don't think I need an inverter duty motor. So I will look into any 1750 3ph, 3HP motor I can find.

    Can anyone tell me what a motor's service factor is? I usually see them at 1.15 or so, but I just found a motor with one at 1.0. Is this of any significance? Thanks

    Hutch

    P.S. Thanks Matt. That is a lot cheaper than what I have been seeing, even on eBay.
    Last edited by Matt Hutchinson; 04-12-2008 at 11:42 AM. Reason: Changed my mind.

  11. #11
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    Here's a good price on a new motor:
    http://www.surpluscenter.com/item.as...tname=electric
    About $106 shipped.

    I might have a nice multi-turn resistor appropriate for the speed control on that TECO drive. If I do and you want it, PM me and I'll send it to you.


  12. #12

  13. #13
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    Good Stuff

    Thanks fellas. I now have enough to go on. I feel confident that I can make the transition without difficulty. However, I am going to sit on it for a while. I just spent my money on another lathe....a Rikon. I still plan on changing drives on my big gal, but it was less of an immediate need. The booth season in coming soon, and I deparately needed to be able to do some spindle turning. But I bet that I will be able to show you the new drive system within a few months. Feel free to keep posting additional important info on this thread...the more I learn the better. Thanks.

    Hutch

  14. #14

    VFD~ word to the wise,

    Matt,
    I did a lot of research into buying my VFD and after talking with several manufacturers they all reiterated the same information. If you have a 3hp /3 phase induction motor and you only have single phase 220 for the power input to the VFD you will need to double the horsepower rating on the VFD - you loose the third leg of input to the VFD (33%) and because of that factor you that is why they "highly recommend" you Double the hp rating. so you should get a 7hp rated VFD for a 3hp induction motor. http://www.cnczone.com/forums/archiv...p/t-17561.html - I would hate to see you spend hard earned money on a VFD that will not handle the load.
    Brian

  15. #15
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    Whew!

    Thanks for the heads up. You may have saved me some serious heartache.

    Hutch

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