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Considering a 3 phase CNC small lathe - - - have 240V single phase

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ajoeiam

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Greetings

Quite new here!!
Have only read a small amount of the threads available but am noting that there is a very large experience band through the group.
Considering a smallish CNC lathe - - - - price is the same as a new 13 x 40 Chinese lathe (I'm thinking the used machine I'm considering is better quality - - - imo anyway!).
The issue - - - - 230V 3 phase is the power required - - - - of course I don't have such (planning an electronic 3 phase converter some time soon but not yet).
Any ideas for a cheap way to get the lathe to run on single phase power?
 

Tim Wescott

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I haven't done this myself, but I used to frequent a USENET group full of home machinists, where I learned this trick. A lot of the guys on that group were retired machinists living in residential areas with single-phase power, who still wanted their 3-phase machines.

Search on "phase converter" -- specifically "rotary phase converter". The short story (which is all I know) is that you get a 3-phase motor, equip it with a starting capacitor and changeover switch.

In operation, you get the converter started, then use it to power your 3-phase equipment. Once a 3-phase induction motor is started, it will generate the other two legs of 3-phase power. The voltage and phase will be a bit off, but unless your equipment has some really picky electronics powered by the 3-phase, you'll be OK.
 

dieselpilot

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Rotary Phase Converter is the typical solution. There are CNC grade RPC available. Whether or not you need CNC grade will depend on how picky the machine is for power. Research about the machine can help here. There is some care to be taken when connecting the wild leg to the machine. You'll want to know how to properly install or hire it out, as you'll likely need a hole new line run and everything that's associated with it.

I missed the part about getting a digital converter, I would just do that from the start.
 

BaronJ

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Greetings

Quite new here!!
Have only read a small amount of the threads available but am noting that there is a very large experience band through the group.
Considering a smallish CNC lathe - - - - price is the same as a new 13 x 40 Chinese lathe (I'm thinking the used machine I'm considering is better quality - - - imo anyway!).
The issue - - - - 230V 3 phase is the power required - - - - of course I don't have such (planning an electronic 3 phase converter some time soon but not yet).
Any ideas for a cheap way to get the lathe to run on single phase power?
The simple answer is go and buy a VFD, single phase in, three phase out. Just make sure that you buy one that is big enough to cope with the machine total power requirements.
 

BaronJ

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I haven't done this myself, but I used to frequent a USENET group full of home machinists, where I learned this trick. A lot of the guys on that group were retired machinists living in residential areas with single-phase power, who still wanted their 3-phase machines.

Search on "phase converter" -- specifically "rotary phase converter". The short story (which is all I know) is that you get a 3-phase motor, equip it with a starting capacitor and changeover switch.

In operation, you get the converter started, then use it to power your 3-phase equipment. Once a 3-phase induction motor is started, it will generate the other two legs of 3-phase power. The voltage and phase will be a bit off, but unless your equipment has some really picky electronics powered by the 3-phase, you'll be OK.
This is a rather inefficient and expensive way of getting three phase power. Ask yourself why electronic VFD's have become so popular!
 

dieselpilot

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If you need to drive a three phase motor a VFD is the answer. If you have a complicated machine which requires three phase input, a VFD will not help.
 

Gordon

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The cheap way to do it is to just use a three phase motor as an idler and put a sheave on the shaft and kick it over with your foot to get it started. Once it is started it generates the other leg. I used that method in my home shop before I retired when I was just using the shop occasionally.

Look at:
 

Gordon

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Interesting story. When I first started in business I inquired as to how much it would cost to run in three phase. It was super expensive because I had to pay to run the line about 1/2 mile so I used the idler motor for quite a while until I hired a few people and it became a problem with running several machines at once so I called to find out much it would cost thinking I would just have to pay it. They informed me that they could upgrade for free. New installations the customer has to pay for. If I had known that I would have called to upgrade the day after they ran in the single phase.
 

dieselpilot

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Take a close look at the voltages at the bottom of that page. Any voltage over 260V will probably trip the drives in a CNC machine. This is why companies produce proper converters.
 

SmithDoor

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I would build a phase converter.
Low cost and simple
This what I do when i need 3 phase at home.

Dave

Greetings

Quite new here!!
Have only read a small amount of the threads available but am noting that there is a very large experience band through the group.
Considering a smallish CNC lathe - - - - price is the same as a new 13 x 40 Chinese lathe (I'm thinking the used machine I'm considering is better quality - - - imo anyway!).
The issue - - - - 230V 3 phase is the power required - - - - of course I don't have such (planning an electronic 3 phase converter some time soon but not yet).
Any ideas for a cheap way to get the lathe to run on single phase power?
 
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rutzen

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I've just converted mine- VFD from amazon for about £60 , easy to install, quiet and you get speed control into the bargain.
 

Jules

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You will need as much information about the machine as you can find.
A rotary phase converter at the correct rating will run it.
A VFD won’t.
VFDs will turn single phase into 3 phase but need to be connected to a load in order to work.
The size you would need to run a decent sized cnc motor won’t be happy powering just the control system.
They are normally connected directly to the motor.
You may be able to run the controls and servos etc from single phase and run the spindle motor from a VFD.
Note. VFD is variable frequency drive......Not supply.
 

BaronJ

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Hi Guys,

A VFD is simply a device that takes and turns a single phase voltage supply into a DC one, chops it up and turns it back into an AC supply with three phases 120 degrees apart to provide a three phase output.

The fact that it has various other features like being able to alter the output frequency and hence motor speed is not relevant to its operation as a three phase power source ! The only constraint would be that the output frequency be set at 50 Hz in the UK or 60 Hz in the USA.

In short it is a simple inverter converting single to three phase power.
There is no magic about a VFD, its just physics !
 

daz59

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My first small cnc lathe I had a phase converter running it. The phase converter would run on 1 or 2 phases and output 3 phase. Ran it for many thousands of hours without an issue.
 

davidyat

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Try going here:
I was very lucky, they were just 10 miles from my house. I built my own rotary converter as a friend had a new 7 1/2 hp moter he gave me. Remember, a rotary converter needs a motor that’s 50% bigger than your machine’s horse power. I had 5 hp machines and used the 7 1/2 hp motor.
Grasshopper
 

Gabe J DiMarino

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I have very limited electrical skills and i was able to go online and download a schematic for a phase converter . Go to local industrial and for about a 100 bucks make a 3hp phase converter .Then ended up going with a 10 hp motor .If I can do it so can anyone , be safe do some research and you will have a very efficient way to generate 3phase power .I run my wire EDM, Mills and Grinders all from one phase all at the same time .One potential relay one start relay one capacitor a few resistor wire nuts a three phase motor 50 percent larger than the biggest motor you want to drive and a box to put all the stuff in.
 

ajoeiam

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My first small cnc lathe I had a phase converter running it. The phase converter would run on 1 or 2 phases and output 3 phase. Ran it for many thousands of hours without an issue.
The machine I'm considering on the nameplate reads that 220V 3 phase 40 A (60 Hz) is the power rating.
40A is not small and it is a somewhat newish machine so I really don't want to let out the 'magic smoke' (grin!).

What was the rating on your machine and what specific phase converter (with model please) did you use.
 

ajoeiam

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Rotary Phase Converter is the typical solution. There are CNC grade RPC available. Whether or not you need CNC grade will depend on how picky the machine is for power. Research about the machine can help here. There is some care to be taken when connecting the wild leg to the machine. You'll want to know how to properly install or hire it out, as you'll likely need a hole new line run and everything that's associated with it.

I missed the part about getting a digital converter, I would just do that from the start.
I'd love to 'just buy the digital converter' - - - that would over double the cost of the machine and I don't have the spare cash at present.
 

dfoster250

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My guess is that the controls run on single phase and the drive motors are 3 phase. Problem solved split the inputs and wire controls to what they need and a converter for the high current drives.
 

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