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Thread: Variable speed motor drive for your tools ...

  1. #1
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    Variable speed motor drive for your tools ...

    ...not quite ready for prime time?

    I tried to scam Greg Cook into finding the answers for me, but he's too busy gloating today

    The idea was to use a variable frequency drive (VFD) with 110vac single phase input to run a 3 phase motor (huff puff) and provide things like variable speed and soft start.

    The answer that Greg and I both found, is that you can buy the VFD's all over the place, but they're pricey - starting price on new units around $400.

    Well, that's fine for those who don't mind tripling the price of their drill press or whatever to get speed control, but it's more than I want to blow on a luxury item.

    I decided to investigate an alternate route - DC motors. The site that really set me on my way is a How-To by a guy who adapted an exercise treadmill motor to his Taig mini-lathe. Everything you need, including part No's is there, so I could stop here.

    But while Greg was waxing his latest restoration, I soldiered on and got updated links for the major components. Read the above link for clues on how to put it together.

    Motor

    Speed Control 1
    Speed Control 2

    Cooling Fan

    Depending on the speed controller you choose, you're looking at $75-85 (+ shipping)

    You'll need to spec out a pulley.

    The problem from my point of view is that you need to shop in at least 3 different places to benefit from these "savings". Then when you get all the bits, you'll need to have a bit of electrical savvy to put it all together.

    Anyone know of a more convenient way of doing this ??

    [apologies to Greg ]
    All the best,
    Ian G

    **Now holding auditions for a catchy new signature**

  2. #2
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    Ian,
    I'm not sure were you came up with the $400 price for a VFD. That's a bit high, actually that's REALLY high for a 110v input/1hp 3ph output VFD. The prices on VFDs has dropped incredibly in the last few years. You can pick up a brand new 110v input/1hp 3ph output VFD from Factorymation for $120. http://www.factorymation.com/s.nl/it.A/id.193/.f. You can find used ones on fleebay and such for a lot less. Used 3 phase motors are a dime a dozen, the market is flooded with them. I payed $25 for a 2hp/3ph that had never been installed. Check the used machinery dealers and scrap yards or the local want adds.

    Refitting your DP with a like framed 3ph motor is going to be a lot easier than trying to rig up a mount and such for a DC motor which will require quite a bit more effort and ingenuity. Just from a time and aggravation standpoint the VFD/3ph setup will be a lot quicker and cleaner.

    The electrical are not difficult. Other than the main power feed, everything Else is low voltage. You can get real fancy and costly using the remote station control boxes from the manufacturer or go bargain basement on the control switches and use simple toggle & potomiter switches from Radioshack.

    Mike

  3. #3
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    Mike, I'm glad you chimed in here, as I was thinking of loading a container full of VFD and shipping them to the US, they are cheap here, used, or slightly used, or even new, cheap.

    Cheers!
    The pessimist complains about the wind; the optimist expects it to change; the realist adjusts the sails.
    William Arthur Ward

  4. #4
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    Actually Stu, they're cheap here too. You just have to spend some time finding them and know were to look. VFDs and 3 phase power are still mostly found in the commercial/industrial realm here. For the hobbyist it can be a bit daunting to venture into the commercial/industrial market place. The commercial/industrial supply places can be a bit harsh with newbies wasting their time and looking to get educated on THEIR dime. As long as you educate yourself beforehand and talk intelligently you'll have no problem though.

    Maybe Don Baer will chime in on this thread to lend some of his expertise and give us some of the pluses and minuses to DC vs. AC motors and VFDs???

    BTW, how much did you say it would cost to ship a container of used VFDs form Tokyo to Hampton Roads? If we could figure out how to get them converted to 110/240v 60hz we'd be in business!

    Mike

    Quote Originally Posted by Stuart Ablett View Post
    Mike, I'm glad you chimed in here, as I was thinking of loading a container full of VFD and shipping them to the US, they are cheap here, used, or slightly used, or even new, cheap.

    Cheers!
    Last edited by M Toupin; 02-16-2007 at 12:20 PM.

  5. #5
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    I think that the ones we have here will work there too, so.........

    Just funning, but nice to know that they can be had over there.

    Cheers!
    The pessimist complains about the wind; the optimist expects it to change; the realist adjusts the sails.
    William Arthur Ward

  6. #6
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    I paid $35 for my last VFD. Then I turn around and fried it. But there is no reason to pay $400. Just check EBay and you can find one for under $150. as Mike said.

    I have set up a DC motor and it works. I found all my parts at the Liquidation Center(?). That doesn't sound right but they had the motor and control for about $150 but you never know what they will have in stock.

    Jeff
    God grant me the senility to forget the people I never liked anyway,
    the good fortune to run into the ones I do,
    and the eyesight to tell the difference.


    Kudzu Craft Lightweight Skin on frame Kayaks.
    Custom built boats and Kits

  7. #7
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    Well, I'm glad to hear this. It's what I expected when I first started searching, but Google searches (and I did plenty) kept leading me to something in the $375 range. I searched online surplus places - and fleaBay too. From what Greg said, it sounds like his results were the same.

    Anyway, thanks for that link, Mike. Could anyone who has a cheap VFD please post the make and model No of theirs ?

    The 3 phase/VFD solution beats the heck out of DC for me. Much less fiddling around with motor mounts.

    I'm glad I found out more about the DC option, though. That treadmill motor could be handy for lots of things. And I've seen treadmills go dirt cheap at auctions. And they have their own inverter/contoller built in... If I ever get motivated to built a mortiser or something (unlikely) I might revisit this.

    Thanks all
    Ian G

  8. #8
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    From motor theory, you could use a VFD to drive a single phase motor (just use one phase of the three phase output). I never hear about people doing this, so maybe there's some reason it won't work. My expertise is in communications and not motors.

    If anyone has used a VFD to drive a single phase motor, please post. If it will work, you could use your existing single phase induction motor.

    Mike
    Ancora imparo
    Go into the world and do well. But more importantly, go into the world and do good.

  9. #9
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    Quote Originally Posted by Mike Henderson View Post
    From motor theory, you could use a VFD to drive a single phase motor (just use one phase of the three phase output). I never hear about people doing this, so maybe there's some reason it won't work.

    Mike
    Hi Mike

    This has come up before. The reason that 3 phase motors are preferred is that they don't have start coils, capacitors or centrifugal switches like single phase motors do. These extra features are not compatable with low speed operation - the start capacitor or winding will stick in start position due to low rpm and burn up.

    Well, that's my civilian take on it anyway
    All the best,
    Ian G

    **Now holding auditions for a catchy new signature**

  10. #10
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    Ok, OK....I've been Attachment 4797 into posting....

    Thanks for the link....those are cheaper than what we've found so far...but still! By the time you get a decent motor, and the controller, you've invested a good chunk of change.

    Here's a used motor listed on craigslist...

    http://seattle.craigslist.org/see/tls/277931220.html

    I sure would like to see some real bargain motors and FVDs.... I'll try to find a surplus place around Seattle, too.
    Last edited by Greg Cook; 09-13-2009 at 03:46 AM.

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