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Thread: Phase converter

  1. #1

    Phase converter

    I purchased a powermatic Model 90 lathe three phase thinking I could just put a different motor and switch to make work in my single phase shop. I found out that the variable speed also needs power. It has a baldor 1.5 hp 3 phase motor on it so what do I need for a converter rotary or static? I'm using the lathe mainly for turning for fun. I have a 1.5 single phase for it. Thanks in advance. Bruce

  2. #2
    Join Date
    May 2010
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    Topeka, KS
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    A variable frequency drive is exactly what you need. Should be able to find one for this application for less than $200.

    Ryan

  3. #3
    Join Date
    Dec 2006
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    Toronto Ontario
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    Bruce, I'm missing something here.

    If you have a three phase lathe that's 220 or 240 volts, all you need to do to make it work on single phase is add a VFD. (Variable Frequency Drive)

    If the lathe already has a VFD, check to see if it's OK for use with a single phase input, many small models are.

    That way you wouldn't have to change anything.................Regards, Rod.

  4. #4
    Join Date
    Jul 2004
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    Get a VFD (variable frequency device). It will convert to 3 phase, and will let you change the frequency, thus allowing additional speed control. A 2 hp model should set you back less than $200. I have one on my Delta HD lathe and it works great.

    Kirk

  5. #5
    I learned something new today. I have used VFDs but it was always 3ph in 3ph out I did not know that they could be used as a converter. Any day you learn something new is a good day.

  6. #6
    Ive been looking into this and saying a VFD is the answer may be premature. As I understand it not all motors will run happily on a VFD.
    ...we could not handle the adze with half his skill:the improvement of tools had lowered the need for personal ability. W. Rose

  7. #7
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    The odds are that a motor won't like a RPC due to the voltage imbalance than a vfd. Many vfd problems with motors relate to the 440V systems rather than the lower voltage. Never say never but there are worse things to worry about. Almost all 3 phase input vfds work with single phase input. Some manuals spell it out, some don't. Check with tech support. Dave

  8. #8
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    May 2010
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    It is my uneducated belief that the voltage imbalance with RPC's is of little consequence on low-voltage, low-power (less than 20HP) loads. Also, as for VFD's being hard on motors, from what I've read, the only real risk is trying to run a standard motor at very low/high frequency. Inverter duty motors have very wide tolerance for frequency/speed and are very well insulated to address additional heat that may not be dissipated at low speeds. I personally use the VFD mostly as a phase converter and only vary frequency slightly to fine tune speeds. A TEFC standard duty motor running at 25 hz likely won't be able to cool down and heat=bad. Don't push the envelope too hard and you should be OK.

    Ryan

  9. #9
    Here's a great, but incomplete PM 90 project (no stripe):

    http://www.sawmillcreek.org/showthre...ion-complete!&

    Mike went through each of the three phase options, and ended up with a very nice setup.

  10. #10
    Join Date
    Jul 2008
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    VFD's will work in most cases, the exception is when the motor has an electromagnetic brake. Those motors create electricity when braking and dump it back into the power supply, a VFD will either trip or more likely be damaged in that instance. On a lathe, its a great application because of the ability to slow down the motor, but as someone mentioned, the motor can overheat if its relying on its own fan for cooling.

    Rotary converters will supply a balanced load until they are run over about 75% capacity.. As they reach their maximum amperage, the voltage on the third leg starts to drop. This is not really a big problem with most woodworking motors, but causes heat and technically shortens the life of the motor.

    You can also get what is usually called a CNC Rotary which is designed to not overload and typically keeps the voltage within 7% of the other 2 legs.

    Not all Rotaries are created, or labelled, equally.. you tend to get what you pay for.

  11. #11
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    Although pricey, the third alternative is the Phase Perfect electronic converter. No motor but similar to a vfd in that it produces all three legs and is balanced within 2%. I switched from a Kay RPC to it as I have machines from 1 to 10 hp and for the first time all machines are running at full strength on balanced power. I am a huge fan. If you run several machines it is worth a look. Dave

  12. #12
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    Quote Originally Posted by David Kumm View Post
    Although pricey, the third alternative is the Phase Perfect electronic converter. No motor but similar to a vfd in that it produces all three legs and is balanced within 2%. I switched from a Kay RPC to it as I have machines from 1 to 10 hp and for the first time all machines are running at full strength on balanced power. I am a huge fan. If you run several machines it is worth a look. Dave
    Hey David. I have the Phase Perfect as well. lol.. I don't promote it because of the cost but its really the creme of the crop in my opinion..

  13. #13
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    Rick, I got lucky and found one that was used-unused- and still in the wrapping. My understanding is that they are a great US company with very good support for their products. I was told of a unit that fell off a truck and the company repaired it for a few hundred bucks. Good word of mouth. Dave

  14. #14
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    Apr 2010
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    midwest
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    So can you give us a ballpark figure at what these units cost?

  15. #15
    Join Date
    Feb 2011
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    Central WI
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    Jim, go on ebay. The units are listed new under phase perfect and better explained on their website. The smallest unit runs 60-70 amps single phase in and 35 amps out on all three legs. Dave

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