Running a small 3 phase 230v 10" manual lathe off 120v single
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  1. #1
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    Default Running a small 3 phase 230v 10" manual lathe off 120v single

    I want to try and run a 10" standard modern utilathe with a 230v 3 phase motor rated for 2.5 amps using a vfd off a 120v single phase outlet. Have never ran a vfd before.

    Is this possible?

    Is it a good idea?

    My other machines are hard wired in but would like to use a vfd on this machine for fine speed control. My reasoning is if I'm getting a vfd anyway why not use it off the existing outlet that's located right behind the machine and save some money by not having a electrician coming out.

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    Should be no problem, just be sure that you get a drive rated for your application, most need single phase 220v input, but they do make 110v input


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    If my memory serves, 2.5amps at 220 3 phase is around 1HP. That’s right at the max for a 110v single phase input for a VFD but still doable. I tend to over-rate my VFDs a bit, but it might be worth that risk because you’d be saving the cost of having an electrician come out to give you another 220v circuit. I’m with ripperj.


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    By the time you get done with all the details, single to 3 phase usually ends up between 2x and 2.5x the current for 3 phase. So 2.5A at 230 3 phase converts out to between 5 and say 6.5A at 230V single phase. that then converts to 13A at 115V, plus transformer losses, assuming use of a transformer for the boost. not impossible,

    The voltage doubler approach may take a bit more.. Still probably OK. With a 20A circuit, you can draw up to 16A on a long term basis, the breaker is rated at 80% of rating for "continuous loads", which is normally considered to be several hours, often 3 or 4 hours straight..

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    13 amps, single phase 120 - but this is for running that 1 hp motor flat-out full throttle.

    Hardly anyone does that. Also 13 amps from a 20 amp branch circuit, well within the 80 percent
    rating for the breaker.

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    A VFD corrects the power factor of the motor on the input, so the input current Is always lower compared to the output current rating, even more so with the voltage doubler because it adds even more capacitance. So looking at AB drives with 115v input, 230V output, a drive rated for 2.5A output has an input current of 9.5A. No problem at all for a standard 15A outlet. The next size up is rated 4.8A output, the input current is 19.2A, which could only work on a 20A circuit if your use is not continuous as described above by JST.

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    The input power factor on a VFD is lousy at low load.

    As the load is increased, the power factor improves. It improves MORE if the capacitors in the VFD are relatively small, just barely enough. The larger the bus capacitors are, the worse the power factor, because of peak charging currents, which boost the RMS input current for a given power.

    A power factor of 0.6 is reasonable at near full power. Might be even 0.7, depending.

    As mentioned, the reason for this is the way the rectifier/capacitor combibation draws current, which is in a series of pulses, each near the peak of the input half cycle. This is SINGLE PHASE, as we are discussing here, The input current wuth a 3 phase supply is much different, because the pulses are closer together due to having 3 phase..

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    West-7;

    I am running a Standard Modern 1334 with a 1 hp 208VAC 3 phase motor through a TECO VFD that uses 120VAC single phase input with no problems. I have an external stop switch, an external potentiometer, and external forward/reverse controls on the VFD. I am very pleased with its ability to run the lathe. I am certainly willing to supply pictures if required, but short answer is yes. It is both possible, and a good idea.

    Peter

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    ** edit: nevermind, my suggestions did not output 230v

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    Quote Originally Posted by West-7 View Post
    I want to try and run a 10" standard modern utilathe with a 230v 3 phase motor rated for 2.5 amps using a vfd off a 120v single phase outlet. Have never ran a vfd before.

    Is this possible?

    Is it a good idea?

    My other machines are hard wired in but would like to use a vfd on this machine for fine speed control. My reasoning is if I'm getting a vfd anyway why not use it off the existing outlet that's located right behind the machine and save some money by not having a electrician coming out.

    It is an excellent idea... first, the lathe spindle is IMO the ULTIMATE application for a VFD in a workshop... and the second, doing so allows you to pick up good stuff, cheap, and make it work.

    I've got several machines that deal with same circumstance, but they're 480v/3ph, and my supply is 240v/1ph... and their motors are in the 3-15hp range... but what I do will work fine for you...

    Get a dry transformer that's indicated as having a primary connection option of 240v, and a secondary of 120v... and about 2.4kva. Wire it backwards to your 120 supply (through a proper contactor or double-pole switch, for safety). The primary winding will then present 240v single phase, which you can connect to two of the three line connections (i.e. L1 and L3) of your VFD.

    You'll need to use a VFD that either allows single-phase in, or can be set to disable phase loss protection. I use old surplus drives that some guys sneer at, because they're very inexpensive and well proven...

    But something you might consider- IF you want to go this route, check your machine, see if that spindle motor will run at 480v.

    Why?
    Because EVERYBODY wants a 0.5-3hp 240v VFD... but NOBODY wants a 0.5-3hp 480v VFD. You can use a 480-240/120 transformer to provide 480 single to a dirt-cheap surplus VFD and run that spindle just dandy.


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