Single phase or three phase?

If you have over a 100 amp service AND the lathe is under 5 hp on the main drive, go for 3p and a vfd. Otherwise single phase.
 
This is over-kill now but, what the heck... Go with 3Ph and a VFD. Be apprised, there are pros and cons. With a VFD and depending on the lathe you get, some tweaking of the wiring might be necessary. With modern lathes that have a control board with relays for safety switches etc, some tweaking will be needed. Also, the FVD's commonly available on eBay have terrible user instructions. You may need to do a little homework to get it configured properly.

I think there's plenty of people here who have been thru this so if you get stuck, help is usually not that far away.



Ray
 
It also depends on what lathe and what you want to do with it? IMOH, if the lathe has a good range of easy to change speeds and you aren't planning to turn exotic materials you may be fine with the single phase motor. VFD's are great (I am run-in 5 in my shop), they give you, phase conversion, speed control, braking, soft start and other features, but as Ray said, there are some cons as well. For one thing, they aren't "plug-n-play" you'll need to wire it into your machine if you want to use the machines controls for stop-start, forward-reverse, etc. You cannot have any switches between the VFD and the motor, all machine controls must go to the VFD which then controls the motor. So hooking it up requires some electrical skills. Another is the cost, and the "it's another thing to possibly break down" factor. To be clear, I'm not trying to steer you away from the VFD, just want give you a clearer picture of what's involved.
 
I have VFD's running lathe and mill but If I were buying a new lathe I would want a 3 phase and a control system from MKSJ.
 
Keep in mind that if you do go the VFD route it's quite likely that all the machine controls will have to be done through the VFD. That means the start/stop, reverse, and speed change functions will now be controlled through the VFD.

I went the phase converter route on my Sheldon mainly because I wanted to retain all those functions on the original control panel. One difference between this Sheldon and most other machines is that the speed control is done with a couple push buttons on the control station, rather than mechanically selecting gear ratios. The push buttons control a 120 volt gear motor at the rear of the machine. The gear motor controls sheaves much like a Reeves drive.

Here's a picture of the machine with the control panel just below the tachometer on the left side. The buttons are, top row left to right, reverse, forward, stop.

The lower row left to right are, speed reduce, speed increase. If your machine has similar controls you'll have to determine how to transfer these functions to a VFD or go a different route.


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3 Phase.

Because I have both a lathe and a mill, and for reasons of cost, I went with a static phase converter. Under $100
http://phaseconverterusa.com/Static-Phase-Converter_c_11.html
Once the motor is running, the converter kicks out. This leaves the motor running on 2 legs of power. Some have stated that this can cause finish issues with a lathe. For this reason, I start the mill and leave it running (serving as a rotary converter) while using the lathe.

I will be receiving a rotary phase converter once its current owner is done with it, but I really have no complaints with the static.
 
MrWhoopee said:
3 Phase.

Because I have both a lathe and a mill, and for reasons of cost, I went with a static phase converter. Under $100
http://phaseconverterusa.com/Static-Phase-Converter_c_11.html
Once the motor is running, the converter kicks out. This leaves the motor running on 2 legs of power. Some have stated that this can cause finish issues with a lathe. For this reason, I start the mill and leave it running (serving as a rotary converter) while using the lathe.

I will be receiving a rotary phase converter once its current owner is done with it, but I really have no complaints with the static.
Click to expand...

At the current time I have a Lathe, a saw, and a mill all running on static phase converters. There has never been a problem with finish on any of the machines. The mill has been on the converter nearly 20 years with no issues. The saw has been on a static converter about 4 years, and the lathe has been on one for about a year, again with no issues.

Having said this I have had a 15 hp rotary converter waiting to be installed for over a year. I need to add another sub panel to power it. Hopefully that panel will be installed within the next couple months as part of a remodeling project. Once that's done I'll install the converter and connect all the 3 phase machines.
 
Check with the manufacture to see if the lathe is available with a 3ph motor and a vfd pre-installed? If so it will save you a bit of wiring and configuration. If not you will need to do a bit of wiring and configuration to get the vfd working with the lathe... nothing too technical.

I would go for 3ph with a vfd myself... I have installed several vfd's on 3ph machines... a lathe is very small bit more tricky because you have to bypass the reversing switch if there is one and wire the vfd directly to the motor.
 
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I have an American Rotary 7.5hp rotary converter powering: VFD controlled full size mill, VFD controlled 10EE Monarch ,and non VFD controlled surface grinder and Clausing lathe.

I really like the fine tuning speed control the VFD affords on the mill and the 10EE. A little pricey but worth it.

The converter lives with my compressor in a separate structure to attenuate the noise.
 
Me too I suggest 3Ph and VFD but there is a caveat!
Get a VFD rated motor. The difference between a standard 3ph and a VFD rated is in the insulation rating of the copper wire used to do the windings. VFD produces high voltage peaks that are often over the insulation rating of the standard motor.
Also the better quality VFD motors have a fan that runs all the time independent of the motor in the case where you may want full torque at 0 RPM or while braking a system.
Having said this... don't worry too much about that! In the case of a lathe you will never stall a motor and if it happens the extent will bee a blown fuse or a tripped breaker! :)
If I was in an industrial environment I would replace the motor for a VFD rated one, but for a hobbyist you will probably never have this problem.
It is just something you have to know and if the motor burn eventually, don't blame the motor, just replace it with a VFD rated one... in 10-20 years maybe!??
 
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