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Thread: Required HP for a Phase Converter

  1. #1
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    Required HP for a Phase Converter

    I am looking at used Sliding Table saws and will possibly be buying a 3 phase unit.

    It is made by Felder and has a 7.5 hp motor on the saw. Would a 10hp rotary phase or a 10hp Digital phase converter be enough to run this saw?

    I may also need to run a 5hp 3 phase Dust Collector at the same time, so if I had both running what size would I need.

    Generically I guessing I'm asking what the formula or process is to size the correct phase converter?

  2. #2
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    This looks like a pretty good overview.
    http://www.northamericaphaseconverte...ase-converter/

    With 12.5hp looks like you’d be at about 20hp, depending on amperage.

  3. #3
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    <p>
    Steve, I went through this recently, but on a smaller scale. The advice I was given and utilized was that you need twice the HP of your largest motor to start it, but you can run numerous motors on the same system up to the HP of the idler. In my case I needed to start a 2.5hp motor, so I got a 5hp idler. So I can run two 2.5hp motors at the same time, but can&#39;t start anything bigger than 2.5hp.</p>
    <p>
    I had some hesitations with going with a RPC but in the end, I&#39;m glad that I did, it ended up being pretty simple and opens up the possibility of other machines for me without having to buy a new device for each machine (up to 2.5hp). &nbsp;</p>
    Last edited by Brian Holcombe; 12-15-2017 at 9:15 PM.
    Bumbling forward into the unknown.

  4. #4
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    It depends on how the rpc is rated. Kay and Arco rate theirs by the largest motor it will start so a 10 hp Kay gets you there, ( maybe a 7.5 but I wouldn't chance it )as does a 10 hp Phase Perfect. The PP is the best choice but about 2-3 x as expensive. Other rpc are rated differently so a 15 hp rpc starts a 7.5 hp motor. You may away with a slightly smaller rpc as a saw isn't very hard starting but better to have a little room. You will need 60-70 single phase amps to run your machine and DC. The PP and a similar sized rpc should deliver 30 three phase amps on the output side. I can run my 12 hp widebelt off a 10 hp PP so it has a little extra capacity. Dave

  5. #5
    I run a hard to start old planer with a 7.5hp motor and a 5hp blower on a 10hp Kay RPC. 60 amps single phase.

  6. #6
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    I ran my shop for years off a home made converter using a old 15 hp motor we got from a local mine. Had a few 5, 7.5 and 10 hp motors running off this at the same time including the 7.5 dust collector. No issues and when we put in 3 phase from the utility there was no difference in start up time or anything.

  7. #7
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    I would say get the largest one say a 15hp,but use it to run a 3phase elec panel which then run your electrical for your machines back to the panel.This is all for the convenience of not having to roll your phase converter around the shop which is what I do.You may go over to Practical Machinist forum they have a whole section on this subject which was a big help for me just to try to understand Static or Rotary converters

  8. #8
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    If you have the budget contact Phase Perfect. I've been using there PT-330 10HP unit in a similar situation. It's been flawless since I installed in 2010.

    http://www.phaseperfect.com/p/t/overview

  9. #9
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    If you don't start both at the same time you will only need one that will start the larger motor

  10. #10
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    Quote Originally Posted by John Kee View Post
    If you have the budget contact Phase Perfect. I've been using there PT-330 10HP unit in a similar situation. It's been flawless since I installed in 2010.

    http://www.phaseperfect.com/p/t/overview
    Since Phase Perfect isn't open what would a 10hp unit typically run? I'm guessing about $2,500 and hoping not more. Thanks for all the information from everyone. Since I'll have multiple machines I intend to wire in the converter and have it feed a 3 phase panel and then run them machines from it.

  11. #11
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    About 4200. Steep but if you can afford, it provides balanced power for all size motors. RPC are balanced for a limited output range. Usually good enough for what we need but PP is balanced for a 1/2 hp motor or 10 hp. Quiet and dependable. I still have my 10 hp Kay as a backup but have not used it in the 7-8 years I've had the PP. You can sometimes find them used but need to find the white ones as the blue ones are no longer supported. If you find a blue one that works for < 1000, it is a fair risk. The white ones will be 2500+ used. Dave

  12. #12
    Need some help

    I have a new American Rotary Amp20 unit. Looks like this

    https://www.americanrotary.com/produ...ew/amp-series/

    Now there is this nice used mahine at 12HP

    https://www.woodweb.com/exchanges/ma...ts/531205.html


    Is there a safe way to use the Amp20 and get this machine?
    Will it work ok?, will I damage or shorten the convertors life?

    Is there some modification that would make it better?

    thanks in advance for any help.

    Jon F.

  13. #13
    Quote Originally Posted by Jon Fiebing View Post
    Need some help

    I have a new American Rotary Amp20 unit. Looks like this

    https://www.americanrotary.com/produ...ew/amp-series/

    Now there is this nice used mahine at 12HP

    https://www.woodweb.com/exchanges/ma...ts/531205.html


    Is there a safe way to use the Amp20 and get this machine?
    Will it work ok?, will I damage or shorten the convertors life?

    Is there some modification that would make it better?

    thanks in advance for any help.

    Jon F.
    Jon,

    Do you have access to the specs from the motor tag on the planer? Specially, what is the Full Load Amps rating (FLA) for the cutterhead motor and any other motors in the planer like a feedworks motor?

    What is the max single phase amperage that AR says you can feed your unit?

    This is a bit of an over simplification, but my Kay RPC has 60 amps at 240V single phase coming in (could take more but that’s what I had available to feed it) and that translates to a 30 amp 240V 3 phase on the output side. I have no idea if that type of conversion math is specific to my Kay unit (which is rated for up to a 10 HP motor as the single largest load or a cumulative/simultaneous HP rating of 25 HP with enough single phase amps being feed in) or not, but I would start there. I would also call American Rotary once you have specs on the motor of the potential planer and ask them directly with the specifics and they should be able to give you an answer.
    Still waters run deep.

  14. #14
    depends on the brand. Delta TME was 10hp roto for 10 HP machine, then two levels of beefing up that up.

  15. #15
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    I believe the dc motor can be added in parallel to the main rotary as another idler motor. thus increasing the possible load. Start the idler first then the dc then the biggest motor last.
    Bill D
    Last edited by Bill Dufour; 05-27-2021 at 11:08 PM.

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