Request for help - using a VFD to generate 3 phase power for a Mori Seiki MS-1250
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  1. #1
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    Default Request for help - using a VFD to generate 3 phase power for a Mori Seiki MS-1250

    Hello

    I am a new member, currently building my machine shop in my garage. I plan on using a Mori Seiki MS-1250, and need to generate 3 phase power (either 240 or 440 volt) to run it. My question is: can a VFD be used to generate the 3 phase power for this lathe? Also, what would be the better brands/models of VFD for this purpose?

    My electrician will be installing a sub-panel in the garage, it will provide single phase 120 and 240 volt power.

    Any help, suggestions, etc. in regard to this would be greatly appreciated, thank you very much in advance.

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    Default Request for help - using a VFD to generate 3 phase power for a Mori Seiki MS-1250

    I am running a 3hp 240 3 phase lathe with a Teco FM50. Input is 240 single phase. Hobby shop, not a production - type setting. It has done nothing but work, very impressed with it. It’s an old motor that is not VFD rated but I often times dial it down to 15 hertz with no overheating what so ever. I had to YouTube the connection as I was overcomplicating the process. Literally wire the motor direct to the VFD, no starter no nothing. The VFD does the rest. Low voltage wired from VFD to a simple on/off for start/stop. It has other low voltage ports for a myriad of other remote control functions. Simple, inexpensive solution to wasteful roto-phase converter. From my experience, for what I do, the product is good to go.

  3. #3
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    The way you describe what you want gives me some slight concerns. A VFD is a device that allows an electric motor to be driven at variable speeds by changing the frequency of the ac power. Many VFDs can operate from a single phase supply and provide three phase to the motor. I would not describe them as being a general purpose "generator of three phase power", although they can do that for a motor of the correct type. You do not just wire a VFD into the main power to your lathe and expect everything to just work - it might but that is not how VFDs are intended to be used. If that is your expectation, you may be better off with some form of rotary converter at the expense of added noise etc.

    I am not familiar with the Mori Seiki MS-1250, except by reputation. I assume you have only one motor on your lathe (the spindle motor), and that motor is intended to be used with 415V supply. This is typical of most industrial lathes (in most countries anyway - the US is a little bit different). If that is the case, in order to use a single phase supply to power the lathe through a VFD, you will need to rewire the motor to run in delta. This will have the effect of allowing a 240V single phase in, 240V three phase out VFD to be able to run it. Not all motors are set up with the capability of being re-wired in this way. If not you may be able to take the motor apart and modify the windings but this is not something to try unless you are fairly experienced. A motor that is designed for both star and delta connection will generally be marked as such on its data plate so you should have a good look at that, preferably take a photo and then report back. If you are lucky, you may have a motor that is intended for 240V, in which case you do not need to rewire it, assuming that you have a real 240V single phase supply.

    As well as the motor there will be other electrical parts. Switches, motor starters etc will be designed to run off three phase supply. You will need to rewire all these to use the low voltage controls provided by the VFD. This can generally be done using most of the original switchgear, but the wiring will neeed to be redone. If you can get a wiring diagram for your lathe, that will give the basic information needed to plan this job.

    If your electrician is a good industrial electrician, rather than just a domestic guy he will be able to give you all the details you need from an inspection of your lathe. He should also be able to do the whole job for you, at a price.

  4. #4
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    I bought a 220v 3-phase mill and put a Hitachi VFD on it. Removed the original factory wiring with reversing switch. Works so good I bought a 220 volt 3-phase motor for my lathe and installed a Hitachi VFD on it, too. I removed all the clap-trap wiring, relays, etc. and made a control panel that gives me forward/reverse, jog, emergency stop, and a digital speed readout (Tachulator). I LOVE it.

    Simply wiring the motor isn't the hard part, trying to figure out the Hitachi manual for all the 24v peripherals and programming it was the hard part. Their manual isn't the easiest to figure out.

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    I can also attest to a Hitachi VFD working perfectly off single phase 240 with a 3hp 208V milling machine and as the folks above have noted, just ditch all the other wiring. I found a brochure here: https://www.sterlingmachinery.com/me...e-brochure.pdf. It says these lathes are 5hp but I recall that should still work though I haven't looked at it for a long time. Presumably this is for a home type application where you don't have many machines running at once. By the way I also recall that 440V is a problem and in fact if you figured out how to get 440V 3ph from 240V I'd love to hear about it.

  6. #6
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    What BILLMAC above says.

    More : unless you buy a substantially larger vfd than you would imagine (like 25-40hp, and yes, it can work), you are not going to be able to use the existing control system on the lathe. To simple "generate 3 phase" A VFD is the WRONG approach to this problem unless you want variable speed, and even then you will need to rewire the lathe internals considerably.

    The EASIEST approach is to buy a Phase Perfect. That will generate "better than utility 3 phase " power from single Phase. About $3k for a 10hp unit. I run exactly that on a similar lathe. If you can run it from 240, you are good to go. If you need 460/480, a 10-15kva transformer is placed after the Phase Perfect. IF you really need 440 (unlikely) a couple of buck transformers are placed before the Phase Perfect. You could also install a rotary converter.


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