Results 1 to 9 of 9

Thread: 3 phase question

  1. #1
    Join Date
    Apr 2009
    Location
    El Dorado, KS
    Posts
    3,352

    3 phase question

    I know you can hook up a 3 Phase motor for a lathe with a VFD to plug it directly into a 220v oulet, but does this same principal apply for a 3 phase piece of equipment like a table saw or sander?

    I found a local auction that has some nice commercial woodworking tools but all of them are 440 3 phase.
    -------
    No, it's not thin enough yet.
    -------

  2. #2
    Join Date
    May 2009
    Location
    N.W. Missouri
    Posts
    1,564
    I don't think you can get a VFD with 220v in and 440v out.


    John

  3. #3
    Join Date
    Dec 2006
    Location
    Porter,TX
    Posts
    1,520
    They will need to be able to wire for 220volt 3 phase,but I think most motors are multi tap 220v/440v.You may want to check and see the motor for yourself.If you are going to purchase multiple machines,I would consider buying one vfd and size it for your largest motor.Mount the vfd so that you can roll it around to the machine that your going to be using.One problem is since your sizing it for your largest motor is the overload protection,it will be rated for the largest motor and not for your smallest motor.But how often does motor drawn more amps really not that often unless they lock up but you will notice problems before it gets to that point.Most of the time a motor will go to ground or earth fault and any size vfd will pick that up in an instant.The vfd in our case is for converting single phase into 3 phase and provide soft start only,so I say it will work on a table saw and a sander but ramp it up to 60hzs.All this is my ideal and I have not done it except on a lathe.Another option is a rotary phase convert to power to power up a 3 phase panel so that you can run 3 phase power to each machine providing that your not running several machines at the same time.----Carroll

  4. #4
    Join Date
    Feb 2011
    Location
    Redmond, OR
    Posts
    606
    There are 3 phase step up transformers that will give you 440v 3ph from 220v 3ph but they are big, heavy and expensive.

  5. #5
    Join Date
    Oct 2007
    Location
    New Hill, NC
    Posts
    2,568
    Check out the motor plates. Most 480 VAC motors can be switched over to 240 3 phase rather easily.

  6. #6
    Join Date
    Apr 2009
    Location
    El Dorado, KS
    Posts
    3,352
    Thanks for the info. Sounds like a little more research is in order before considering bidding!
    -------
    No, it's not thin enough yet.
    -------

  7. #7
    Quote Originally Posted by John McClanahan View Post
    I don't think you can get a VFD with 220v in and 440v out.


    John

    You can get VFDs that take 120 and out put 240/ 3 up to 1.5 hp and then there are drives that take 240 and convert to 420/3 they cost about 2 times as much as the common drives
    jack
    English machines

  8. #8
    Join Date
    Dec 2010
    Location
    Toronto, CA
    Posts
    320
    Scott

    I've been playing this game for the past year and learned a few things:

    1 - 3ph motors are really cheap,easily available , so might as well use them on multiple machines. I now have 5 machines on 3 ph.
    2 - Phase converters are cheap. WNY has them <$200 for up to 10 hp. Add a motor and you have a rotary phase converter. I've heard that you need special this and that, but I just used whatever 3ph motor I picked up cheap. No issues so far
    3 - once you have 3 ph in, you can get VFD's etc in many sizes, much cheaper. The phase inverter models are more expensive and trickier.
    4 - single phase typically tops out at round 3 hp. I've see a few at 5 and 7.5, but the current draw is insane (~40 amps) and you'd need all kinds of special wiring. And those 1ph are really expensive.

    Before I got my RPC, I bought a Hitachi VFD with 1ph -> 3ph and 3 HP. But that seems to be the upper limit and I frequently overload it with my lathe. The inverters take a hit in HP output actually Amp output.
    There are many on ebay, straight from China, that are cheap and get decent reviews. Haven't tried them, but might if I upgrade my lathe to 5 hp.

    BTW - if those machines have 440v, you might be able to swap out the motors for 208 - 230v. Those 440 sell cheap because no one can use them at home / hobby, for all the reasons above.
    The only tool I've found that needed a really special motor was a Unisaw, the rest are typically a standard mount.

    I've got a WNY RPC, its been flawless and very happy with the setup.

    I tried going the transformer route to get to 575 (used here). They are available, but it was highly confusing (even with copious advice from an industrial electrician) and expensive.

    So i would have had wiring for:
    - 110v 1ph
    - 220v 1ph
    - 208v 3 ph
    And then also 575v 3ph?!? That's just too much.

    Didn't bother going forwards.

    3 ph wiring is not that complicated. Switches and plugs off Amazon, are cheap.

    Hope that helps
    Olaf

  9. #9
    Join Date
    Nov 2012
    Location
    Southwestern CT
    Posts
    1,392
    I thought you could get 440 by using a single-phase step-down transformer (appropriate kw) in reverse, and then converting the 440 from single to 3-phase via vfd. But a search of current vfds doesn't turn up any 440/460 volt that handle a single-phase input. More searching is required - does anyone have a recommendation for a 3hp single-phase input (3-phase output) 460 volt vfd?

    For my setup (I have some 440 only equipment) I take the rpc 3-phase output and run through a 3-phase step-down transformer (in reverse) and that works fine. I already had the rpc, but finding the right transformer was more challenging. I eventually (after months of research and hunting) picked up a GE transformer for less than $100 that had the taps I sought. That made the package pretty palatable from a cost perspective. Single-phase transformers are simpler (one coil), lighter and conceptually at least ... less expensive.

    Using the vfd (if you could find the appropriate model) would provide greater motor control (variable speed, jog, braking, slow-start, etc.). Folks have told me that some building inspectors get nervous when they see a bunch of transformers around a shop. Mine did not.

    One possible issue ... my single phase voltage varies quite a bit, and as a result, so does the output on the transformer. It is not unusual to get 460-465 volts at certain times during the day.

    Practical Machinist has lots of in-depth information (and experts) on voltage and phase conversion.
    Last edited by Bill Adamsen; 03-28-2015 at 11:04 AM.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •