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Thread: Phase converters.

  1. #1

    Phase converters.

    I'm sure this has been covered many times but I think my question is more specific than I am finding answers to by searching.

    I have been looking for a jointer planer combo machine in the 12" range. I recently came across a 20" felder for a decent price that I am considering. It has a three phase 7 1/2 horse motor.

    My garage shop has a 60 amp subpanel. Do I even have enough power to run this thing and lights and dust collector?

    If I do have enough power what would be the best way to get three phase for that motor? Rotary? Vfd? Where's a good please to buy from. I'd like an idea how much this will cost.

  2. #2
    I'n no electrician, but a good rule of thumb for single phase electric motors is 10amps/hp at 120, or 5amps/hp at 240. So, not counting startup surge, you'd need about 35-40 amps of your 60 amp subpanel.

    VFD in that size to convert to three phase would be expensive as you'd have to markedly upsize it. A static phase inverter might be a better choice as they're cheap, but you do take a hit in efficiency and loss of hp. A rotary phase convertor would be best though you would need at least a 10hp idler motor and possibly a 15. You might also consider just replacing the existing motor with a single phase one. One that size isn't cheap, though they do show up on CraigsList from time to time. I got a 10hp single phase Baldor for $200 last year, so they can be found.

    If you decide to go with a rotary, there are tons of websites all across the web to help in designing/building one (commercial ones can be pricey). I attempted to load a pdf of the Fitch William convertor, but it is too large a file. You can either Google it, or if you PM your email I can send it directly. I also found a PDF on static inverters.

  3. #3
    Starting that motor is likely to be a problem, replacing with a single phase motor would be better IMO if the machine is belt driven. If it is direct drive, consider what you would do if the motor failed.
    _______________________________________
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  4. #4
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    I have a static converter on my 5hp engine lathe and a 2hp milling machine, both start up just fine. I've been using this setup for over 20 years.
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  5. #5
    I have a 7.5hp single phase compressor that required a 60A breaker, so you might be up against the limits of your wiring.

    Many VFD's have a "soft start" adjustment, and I've read that there are also "soft starters" for folks already owning a rotary phase converter. In your situation I think without something controlling your inrush current you will overload your 60A panel.
    http://www.lselectric.com/soft-start...quency-drives/

    Also, the VFD's and phase converters for motors above 3hp climb quickly in price, so look at the complete package price. You should talk your situation over with a specialty business such as these:
    http://www.factorymation.com/
    http://www.wolfautomation.com/

  6. #6
    That seems to confirm what I thought. It would be pushing the limits of my current electrical system and add a decent dollar amount to get this thing to run on single phase.

    Guess I'll keep looking. Thanks guys!

  7. #7
    A rotary phase convertor is far better than a static one, as the latter will coast you 1/3 or your horsepower.

    Price will be very high, so yes watch CS.

    -------------------------

    IMO, the cost of VFD's today makes the thought of a huge RPC a little antiquated. A dedicated VFD offers several advantages:

    Only 1 on-off switch

    Easy to add E-stops

    Soft-start - In your case, this might be a life-saver, since inrush current could cause trouble with your 60a mainbreaker.

    Dynamic braking

    Motor reverse

    Vari-speed

    Extra motor overload protection.

    Protection from accidental turn on, as with a Mag starter

    No need for a GFI outlet.

    ---------------------------

    Go to http://www.factorymation.com for the best prices on the planet. Then call and talk to "Dianne" for lots of extremely good tech advice.



    update: I see Paul already beat me to it. Well, it's still all correct !
    Last edited by Allan Speers; 06-18-2015 at 1:45 PM.

  8. #8
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    Since we are talking phase converters, the logical assumption is the supply is 220VAC single phase. As stated the motor in question is 7.5hp 3 phase (voltage not given).

    When I was looking for single phase in-three phase out VFDs, I thought I read something about the highest HP VFD available for this application is 2HP. Is there available a 220VAC single phase in-three phase out 7.5HP VFD available?
    Last edited by Anthony Whitesell; 06-18-2015 at 2:57 PM.

  9. #9
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    Quote Originally Posted by Anthony Whitesell View Post
    Since we are talking phase converters, the logical assumption is the supply is 220VAC single phase. As stated the motor in question is 7.5hp 3 phase (voltage not given).

    When I was looking for single phase in-three phase out VFDs, I thought I read something about the highest HP VFD available for this application is 2HP. Is there available a 220VAC single phase in-three phase out 7.5HP VFD available?
    Not cheap, but, yes: http://www.driveswarehouse.com/p-2124-pc1-75.aspx
    Beranek's Law:

    It has been remarked that if one selects his own components, builds his own enclosure, and is convinced he has made a wise choice of design, then his own loudspeaker sounds better to him than does anyone else's loudspeaker. In this case, the frequency response of the loudspeaker seems to play only a minor part in forming a person's opinion.
    L.L. Beranek, Acoustics (McGraw-Hill, New York, 1954), p.208.

  10. #10
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    Man a 20" Felder would so be worth a panel upgrade if needed!
    Glad its my shop I am responsible for - I only have to make me happy.

  11. #11
    Quote Originally Posted by Mike Heidrick View Post
    Man a 20" Felder would so be worth a panel upgrade if needed!
    I would love to have it....but I would be stretching my budget already just to purchase the machine, and then I would still have to buy a phase converter and upgrade that power to my house. I only have 100amp main coming into my house from the power company. At the time I had the subpanel put in they said 60 amps for the subpanel was about the most they could do from a 100 amp main.

  12. #12
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    I upgraded to a 200amp panel last year when I had refrigerated air installed. The panel upgrade was $1500. That included running a new 50amp line to my shop sub panel.
    Please help support the Creek.


    My wife asked me to take her to one of those restaurants where they make the food right in front of you. So, I took her to Subway and thatís how the fight started.

  13. #13
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    Check out this site http://www.temcoindustrialpower.com/...duct_Selection
    You should be fine, unless there is some other big draw on the panel besides planer and dust collector. I have a 60 Amp sub panel with almost identical power draw and it's all working just fine. Having said that, if you think you can shove a 20" wide oak plank through the planer and hog off a 1/4" think again, just use common sense. You can't compare an air compressor to a planer or table saw, the compressor always has to start under heavy load - the jointer/planer not. Btw. keep the wiring short and heavy.
    I'd bend over backwards to get that machine.

  14. #14
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    60 amp single phase should be enough to run a 7.5hp PH-3 motor .. 3 phase motors aren't as in-rush sensitive as single phase, and the Felder will ( should ) have a Star - Delta starter.. The initial inrush shouldn't be an issue for a second or so ..

    Technically 60 amps should provide you with 34 amps of PH-3 .. but it won't .. so figure 27-28 amps.. A 3 phase 7.5hp motor will draw maybe 20 amps at full load ..
    Last edited by Rick Fisher; 06-19-2015 at 2:38 AM.

  15. #15
    Quote Originally Posted by John Lankers View Post
    Check out this site http://www.temcoindustrialpower.com/...duct_Selection
    You should be fine, unless there is some other big draw on the panel besides planer and dust collector. I have a 60 Amp sub panel with almost identical power draw and it's all working just fine. Having said that, if you think you can shove a 20" wide oak plank through the planer and hog off a 1/4" think again, just use common sense. You can't compare an air compressor to a planer or table saw, the compressor always has to start under heavy load - the jointer/planer not. Btw. keep the wiring short and heavy.
    I'd bend over backwards to get that machine.
    So a static converter like this would work? Seems like I am missing something, this seems to cheap?
    http://www.temcoindustrialpower.com/...rs/PC0013.html

    I have been watching it on craigslist for awhile and have been thinking about making a lowball offer as that is the only way I could afford it. I imagine it is a tough item to sell since its 3 phase, so I was hoping I could get a deal on it.

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