Changing a 3 phase motor to a Single phase motor will it work ?
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    Default Changing a 3 phase motor to a Single phase motor will it work ?

    I have a Chinese version of a lathe with a 5 hp 3 phase motor and was thinking about changing the motor to a single phase 3 hp Dayton. But the question is will the reversing and magnetic switching still work. Sorry if this is an obvious question but I am a nubee.

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    Contactor to start motor will work normally but reversing a 3 phase is just reversing two phases on a second contactor. Reversing a single phase motor involves reconnecting the start winding leads which may need a 4 pole contactor.
    A 5 hp 3 ph motor can be run on single phase by using a 10 hp VFD for many VFDs Hitachi being one. You need the bigger VFD because single phase current will be higher and you are only using part of the diode bridge. Also single phase voltage ripple is much larger needing the bigger capacitors to handle it. Add a braking resistor and the performance will be much more productive than the single phase motor for a tiny amount of extra money.

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    Generally no, and not without a lot of rewiring of the control system

    The three phase motor reversal is accomplished by swapping the connections on any one phase, usually with a contactor pair. Single phase needs the start winding reversed and the motor stopped before changing.

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    Biggest drawback is single phase needs to slow to about 500 rpm before reversing. Above that rpm reverse power will just make it go faster in the same direction. They do make single phase instant reverse motors but a vfd is cheaper.
    You can run your 5hp motor from a cheaper 3hp vfd but it can only supply 3hp from the motor.
    BIL LD.

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    Thanks for the reply I will assume my task of changing to a static phase converter. I'm not getting the response I expected out of the starting switch so it is back to the drawing board to figure out why.

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    Thanks Gary I bought a Static converter but for a 5hp motor it sounds like I need a higher hp converter to make this work not sure what the braking resistor is or how to use it but maybe Phase-a-matic can help Thanks again.

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    If it’s not a CNC lathe, I don’t think you really need a phase perfect.

    I asked tons of questions about this earlier. I’ve done one rotary converter for a Bridgeport costing me absolutely nothing since we made it from scrap.

    The one I just installed was for a Fanuc Robodrill, and this time I bought the converter panel from American Rotary. It powered up fine so far, and from what I’ve heard the problem is usually issues with the control panel. A $20 rotation meter and a $150 used 15HP motor, total cost was about $560. Way different than the $3600 phase perfect wanted.




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    A VFD would be the simplest solution and not change the motor. Contact Automation Direct for VFD's and good tech advice from their experts.

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    I have a complete shop with motors from 1 HP to 10 HP running on a simple RPC made from a three phase motor, very simple to do and has been working great for me for the past 10 years! No problems and cost is very low. Lots of cheap 3 phase motors available.

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    The use of a VFD would give a lot more flexibility, but would require changes to the control system if there are any features other than start/stop and reversing(e-stops, limit switches, etc.) An RPC would be plug and go for the lathe.

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    Go to the transformers, phase converters and VFD forum. This issue has been debated to death there, as much material as you will want to read.

    Bill


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