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Single phase or three phase?

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Mans Racing

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#1
I’m thinking about purchasing a new Lathe and it is available in both single and three phase.In my shop I have single phase power only.Is it better to use a three phase unit with a phase converter or just order single phase unit and be done with it?
Thanks
 

dlane

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#2
If I were in the market ied go three phase and a vfd.
Welcome aboard
 

682bear

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#3
3 phase is supposed to be a lot more efficient... you get more power with less energy used. Or so I hear... I'm no electrical genius, so I just go by what I'm told.

-Bear
 

pstemari

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#4
Three phase allows for simpler motors—no starter caps, etc. Any efficiency gain, however, is going to be wiped out by the VFD. However, unless you're running a full time machine shop, I doubt that matters. The real advantage is being able to fine-tune the lathe speed without stopping and changing gears.

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Bob Korves

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#5
Get three phase. The motors are more robust and have less to go bad. They run smoother. You can hook up a rotary phase converter to make it run, or a VFD to make it run and do a lot of other good stuff. I say go for the VFD unless you plan to be running other 3 phase equipment as well and don't care about the bells and whistles.
 

Bob Korves

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#6
Any efficiency gain, however, is going to be wiped out by the VFD.
The amount of heat coming out of a VFD is pretty small, which tells me they are efficient.
 

dlane

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#7
I was told a phase converter is less efficient than a vfd
 

Z2V

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#8
Another vote for three phase and VFD.
 

JimDawson

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#9
Yup, 3 phase and a VFD :)
 

Ulma Doctor

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#10
with high relative quality and low relative price, the VFD and a 3 phase motor is the way to go
surface finish greatly improves when 3 phase motors are used
you'll be omitting the lathes OEM motor control system, but it is pretty easy to add features you may wish
 
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cvairwerks

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#11
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.
 

Ray C

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#12
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
 

Eddyde

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#13
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.
 

3strucking

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#14
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.
 

projectnut

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#15
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.


IMG_0455.JPG

IMG_0167.JPG
 

MrWhoopee

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#16
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.
 

projectnut

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#17
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.
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.
 

MikeInOr

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#18
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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MattM

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#19
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.
 

blue_luke

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#20
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!??
 

derf

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#21
If you are just a beginner/hobbyist, go with single phase and plug and play. If you are going to use this more than once a week, go the other way.
 
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f350ca

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#22
I'd personally get the lathe with a single phase motor and avoid the hassles and expense of a phase converter.
I bought my first lathe with a single phase motor, then a bridgeport clone mill single phase with variable speed belt drive. No need for 3 phase. My whole cabinet shop runs on single phase as well.
That being said there are times 3 phase is a necessity. I bought a large lathe with a 10 HP motor, single phase wasn't an option so I installed a Phase Perfect converter to run it.
When I replaced the first lathe with a Colchester Student I converted it to single phase rather than run power to it and have to start the phase converter every time I used it.
That was latter replaced with a Hardinge HVL, single phase wasn't an option as it uses a precision balanced two speed motor that couldn't be replaced. At that point I had to install a 3 phase panel to power the Hardinge with lower current breakers.
I latter added a surface grinder. It was 3 phase but the panel was already there so powering it was easy.
Latter acquired a radial drill that was gear drive so not easy to convert to a single phase motor. I used a VFD on it rather than run 3 phase lines to it and have to walk across the shop to start the phase converter. But I only use it as a phase converter, the drill has 8 speeds on its own so no need for the variable function.
The Phase Perfect acts like a solid state rotary phase converter not caring about switching loads or motor sizes up to its limit, so machines are easy to run with it not having to alter any of the electrical controls.
Sometimes you can't avoid 3 phase but if you can why bother with it.

Greg
 

projectnut

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#23
I guess the main reason I look for 3 phase machines is that in our are they are more plentiful, and less expensive than single phase machines. Most hobbyists either aren't familiar with, or don't want to deal with heavy industrial machines that use 3 phase power. That situation is not lost on those selling primarily to hobbyists. Similar capacity single phase machines are almost always more expensive. Not to mention industrial grade machines are built to higher standards.

I'm a bit spoiled having used industrial grade machines for the better part of my life. I like the accuracy, speed, and power of industrial grade machines. There is another thread running about a finish on an aluminum tube. One member was questioning whether his machine was capable of making a .010 deep cut. On any industrial machine that would be close to if not a finish cut. A heavy cut could be somewhere north of .250.

To me the willingness to deal with 3 phase power makes the pool of available machinery far larger than those only willing to consider single phase machines.
 

lcrepairs

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#24
I’m thinking about purchasing a new Lathe and it is available in both single and three phase.In my shop I have single phase power only.Is it better to use a three phase unit with a phase converter or just order single phase unit and be done with it?
Thanks
I would never go 3 phase unless you have to. I have a mill and lathe both single phase, smooth and powerful.

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kd4gij

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#25
Well we have 2 BP mills at work both 2hp one single phase and the other 3ph. side by side. No comparison 3phz hands down
 

lcrepairs

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#26
Well we have 2 BP mills at work both 2hp one single phase and the other 3ph. side by side. No comparison 3phz hands down
Would be great if you have the service. Not worth the extra expense to me to make FAKE 3 phase power.

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100LL

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#27
I’m happy with my 3phase lathe and roto-phase converter. I’ve never used a static converter but have been told they’re inferior to rotary phase converters which create that third phase.

My mill is single phase, and since I have the roto phase I’ve thought about putting in a 3phase motor but, well, there are more important things on the list.

Worst thing would be having no motor at all. It’s a good decision to get to make.
 

Chipper5783

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#28
Are you thinking there will be any more machines in your future? If you are intending to get more machines, are you thinking of purchasing new?

Industrial machines from about the 1950's forward are very nice and widely available (at least in some places) - they are nearly always 3 phase and will often have multiple motors.

If you are purchasing new you will often get to choose single phase or three phase (same as what you are doing now). Of course what ever you finally choose, no reason you can't go down the other path at a later date.

I have about 9 (?) three phase machines connected and running (probably 15 different 3 phase motors) - I don't think it would be practical to run them on some sort of a VFD system. I have one drill press (3 phase) running on a single phase supplied VFD (it worked out easier in my shop arrangement and how the power was set up originally).

I am running all the machines off a 5HP rotary phase converter (my largest motor is 5 HP). It works awesome - I can just keep on plugging in more machines. It is true that the rotary units make a "fake" 3 phase power, but it works great and I have never had a problem.

There is a more deluxe option which has not been mentioned - using a Phase Perfect to get 3 phase power from a single phase source. Again, you can just keep on plugging in more machines to the capability of the unit. With a PP, the power quality is excellent - generally better than grid 3 phase as the voltage control is managed on site and not subject to the vagaries of the distribution system.

The VFD option is a good solution, but it is not "plug and play".

It really comes down to what you want to do with your machining. If you only plan to get the one machine (and with just a lathe and the usual small machines and work space + tools, you can have a very nice & capable shop). Lots and lots of iron really is not necessary to do much good work.

Single phase or 3 phase are both good options. If you are just doing an opinion poll - I'll put in my vote for 3 phase.

David
 

MattM

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#29
I'd be in the three phase camp. I paid $500.00 for my 7.5hp American Rotary converter. Had it for over three years and am very pleased. No problems. Of course I only run one machine at a time since there is only one of me in the shop at any time.
 

682bear

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#30
Please explain the meaning of 'fake 3 phase' in regards to an RPC...

-Bear
 
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