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

I had a small (1HP) CNC machine I rewired to single phase. I determined, from the schematic, the only three phase consumer was the optional coolant pump. My current machines require three phase.

There isn't any need to separate the controls. With a converter, the single phase is just fed through. You'll need to pay attention to this and the generated (wild) leg when connecting phases to the machine.

40A three phase is 69A from single phase. Not such a small lathe, 20 HP? If it pulls a lot of current to accelerate the spindle, you may be able to change parameters to reduce acceleration.

Start with google to see what you can find about running your specific machine from single phase and a converter.

My comment about upgrading to Phase Perfect is only that an RPC will already be a at least 25% of the cost.

How long has this machine been without power? Is the battery in the control still good?

ajoeiam said:

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.

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That is 8 Kw ! 60Hz is the mains frequency.

BaronJ said:

This is a rather inefficient and expensive way of getting three phase power. Ask yourself why electronic VFD's have become so popular!

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The folks I knew who were doing it would get a big 3-phase motor on the surplus market, capacitor and switching ditto, and put together the bits themselves. Inefficiency doesn't matter that much if you're only an occasional user of the dingus, and cost can go down with the application of some cleverness and time spent shopping.

But yes, today, if you're buying it new for a piece of shop equipment that needs to run all the time, an electronic dingus is probably better.

And a VFD puts things into a whole different class -- but if you're driving a CNC, I would assume that there's already a VFD driving the motor, under control from the CNC controller. That VFD would want a constant-frequency input.

BaronJ said:

That is 8 Kw ! 60Hz is the mains frequency.

Click to expand...

You'll want to check the math, keep in mind this is three phase.

[

dieselpilot said:

You'll want to check the math, keep in mind this is three phase.

Click to expand...

Yes you're right ! Nearer 15.25Kw.

ajoeiam said:

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.

Click to expand...

I will look on Monday. 40amp per phase? Thats a reasonable size machine, my big lathes I currently have, have a max rating of about 55amp per phase, 50kw ish and 60kva (im running on 3 phase now). If your machine is that big (40 amp) you are going to need a rather large phase converter, somthing that can handle 30kw+, you will need at least a 120amp single phase supply. My one was 10kw and rated for cnc’s it balanced the voltage output to +/- 5% if I remember correctly.

Do you have a link to your machine?

BaronJ said:

Yes you're right ! Nearer 15.25Kw.

Click to expand...

I get 26kw, 40amp per phase, so 8.8kw x3

dieselpilot said:

I had a small (1HP) CNC machine I rewired to single phase. I determined, from the schematic, the only three phase consumer was the optional coolant pump. My current machines require three phase.

There isn't any need to separate the controls. With a converter, the single phase is just fed through. You'll need to pay attention to this and the generated (wild) leg when connecting phases to the machine.

40A three phase is 69A from single phase. Not such a small lathe, 20 HP? If it pulls a lot of current to accelerate the spindle, you may be able to change parameters to reduce acceleration.

Start with google to see what you can find about running your specific machine from single phase and a converter.

My comment about upgrading to Phase Perfect is only that an RPC will already be a at least 25% of the cost.

How long has this machine been without power? Is the battery in the control still good?

Click to expand...

Now im starting to question my knowledge. How are you getting 69amp single phase if 3 phase is 40amp? That would make sense if phase to neutral was the same voltage as phase to phase. Over here our single phase is 240volt, 3phase is 420volt. So the 3 phase splits the current draw in 3.

According to my Ugly's Electrical Reference book, at 230V the full load amps of a 15HP motor is 42 amps, and if I did my math right that 40A at 240 volts translates to about 9.6KW for those of you that are more metrically inclined.

I don't know of anybody that makes a VFD rated for 15HP output with a single phase input. From what I've seen, those units pretty much top out at a 5HP rated output.

Pretty much any 3 phase VFD can be powered by single phase, but there are tricks you need to do to the drive, so it's not just a simple plug and play. When a 3 phase VFD is powered with single phase you also need to de-rate the drive, by half is the normal practice (It's that square root of 3 thing for three phase. It's 1.73-ish, but in this case 2 is close enough.). This quickly gets you into the area where you can't just go out and find an inexpensive VFD anymore. In this case with a 15HP output required, you'd need to start with a three phase drive rated for 30HP.

Don

Back about 30 years ago I bought a 14 inch X 36 " lathe, 3 phase, from a welding shop in the city. I live on a farm with only only single phase 240. I put together a phase converter I had read about in a magazine. I got a 5 hp 3 phase motor, wired it up to the lathe and to my 240 volt. Used a 3 hp 120 motor with a v belt to bring the 3 phase motor up to speed, then turn the bigger motor on to electric and away it went. A small machine shop about 30 mile from me had a 100 hp 3 phase motor that they had a large pulley on the end, wrapped a 50 ft rope around the pulley, had 3 men run 50 ft pulling the rope to bring the 100 hp motor up to speed with a 4th man to turn the electric on. Old rural people have ways to do stuff. I have seen articles on the computer and you tube of simailar set ups

Hi
The largest industrial grade VFD I could find, purpose built for single phase input, is rated to 3.8kW at 240VAC. It is one of the Yaskawa V1000 series VFDs and I have one fitted to my Nardini lathe. Yes you can de-rate a 3ph VFD, but you are paying for hardware that you won't use.

Also, I have not been able to load up my lathe to max power using modern carbide tooling running under rated cutting conditions.

I am an Electronics Engineer, so I have completely changed out the motor, protection and control system. The only original electrical component is the apron operated fwd/stop/rev switch.


Here is my lathe as delivered. It was fitted with a 400VAC, 3ph 6.8kw dual speed motor.
I replaced the motor with a new 240VAC, 3phase 4kW version.
I also replace the coolant pump with a 1ph 240VAC version.


This is the enclosure I made with the VFD, protection and control system installed.


I added this control panel to provide the extra functionality I added to the control system. This includes:

• jog fwd/rev,
• power,
• e-stop,
• variable speed,
• power meter LED bar,
• rpm counter.

The panel is bolted to the place the work light originally fastened to.

In addition, I added safety interlocks and also a second e-stop by the tail stock




Here the laptop is being used to tune and control the VFD. This is not a normal mode of operation for me.
I replaced the original incandescent control lamps with modern LED versions. The LEDs are similar in size and style to the original lamps, but look way cooler.
The 3 position switch selects preset speeds at red and blue that match the gear selector RPMs. I can use the motor speed selector and gears as if it still had the original 2 speed motor.
The green LED position selects fully variable speed. I can adjust the motor speed to anything I want.



The retrofit was done in a way that made the whole installation look like it was factory installed. I am very fussy like that. Good engineering should look good.

Also the control system is setup to allow for the future installation of a CNC retrofit.
Basically an electronic version of a hydraulic copier attachment.
All of this is only possible because of the ready availability of good VFDs.
I purchased my VFD from www.motorcontrolwarehouse.co.uk. They are much cheaper than USA prices.

You don't need to be an Engineer to do this (it does help). All of the information is contained in the manual.
A properly installed VFD makes an old manual machine like this much nicer, safer and easier to use.
You need to ensure you comply with local electrical regulations.

Dazz

dazz said:

Hi
The largest industrial grade VFD I could find, purpose built for single phase input, is rated to 3.8kW at 240VAC. It is one of the Yaskawa V1000 series VFDs and I have one fitted to my Nardini lathe. Yes you can de-rate a 3ph VFD, but you are paying for hardware that you won't use.

snip

Dazz

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Very nice build.
If I could find a lathe like you have I would be all over it.
Rather what I could find - - - - so far (haven't bought yet!!) is this CNC/Manual lathe.
Not my first choice but the price is right if I can figure out how to connect it to the power I have available.
Have been looking into VFDs for some other projects but haven't worked with nor run them.
Sound like a great idea - - - - am concerned about longevity though!
Electronics seem to be quite ephemeral compared to iron - - - - grin.

I gone several routes.... I have built a phase converter using a 3 phase motor and capacitors for tuning. This works well but does consume some power when you are not using shop motors. It also can be a little noisy. I ended up moving the idler outside in a small hutch (dog house type thing), which worked well.

For small motors, I've used the VFD route. You should be aware that this only works for motors that are about 3HP or smaller, though. And you should over-rate your VFD. Finally, not all VFDs will work; look for one that says it can take a single phase input or call the manufacturer. Although it is true that ultimately the three phase is rectified and put onto a high voltage DC bus (from which the three phase is generated), some VFDs sense the input legs and will fault if it doesn't see everything.

The last route I've gone is a Phase Perfect. This is probably your best solution for larger machines or, arguably, CNCs that require a transformer. What does that mean? I'm in North America where my power is 220V. I have a European CNC that is 380V three phase. It has its own custom VFD built into it and choosing the legs that powered the control simply was not possible. I *had* to have a step up transformer. I had difficulty getting the rotary to work well because the control had sensitive lead/lag detection circuitry. I finally went with a Phase Perfect. These are essentially VFDs that are designed specifically for loads to be switched on and off. That means they are intended to act in a way where they can be connected to a load panel and supply the whole shop. They can also work with 10HP motors or more. Sadly, Phase Technology has the patent on them and they really do want to collect the money. You can expect to pay 2K for a setup.

One word of caution. If you choose to use a traditional VFD as a phase converter, DO NOT put heaters or any other interrupter (switch, protection) after the VFD. Simply put, unless the VFD is designed for it (only Phase Perfect, as far as I know), it will *not* tolerate loads being switched off. The VFD acts as the switch and the protection device (through parameter settings). This is why you can't use a large VFD to power a whole shop, switching different loads on and off... You'll kill your VFD if you try that.

Dazz.... I'd hire you! That is a nice retrofit job. I'm an EE too (although I went to the dark side and now do software primarily), and I'm ashamed to admit it but.... My retrofit didn't look that nice. That said, usually it is pretty close. Anyhow, kudos on a nice job! VERY nice job.

MrMetric said:

Dazz.... I'd hire you! That is a nice retrofit job. I'm an EE too (although I went to the dark side and now do software primarily), and I'm ashamed to admit it but.... My retrofit didn't look that nice. That said, usually it is pretty close. Anyhow, kudos on a nice job! VERY nice job.

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Hi

The Nardini is only my 2nd VFD conversion.
The first was my Denford Viceroy you can see at this link .

This was intended to look factory installed as well, although when the Nardini and Denfords were built, no VFD existed.

I know everyone has different skills and requirements, but I cringe when I see a VFD hanging off the wall. VFDs are designed to be fully integrated with the machine. If you are not throwing out the entire electrical system, except maybe some switches and the motor if you are lucky, you are not doing it properly.

Dazz

Agreed, although not everything has a large electrical box as you have shown. That seems to be more of a European thing, unless you are talking about CNC machines. My Deckel is old, but even it has a large box (well, lots of reasons why they did it, but the point remains that it is a 60's machine). In my case, I went down the route of a Phase Perfect, so I don't change out the three phase at all.... I just plug in and go. But that is a Cadillac (OK, you are British... You probably would say 'Rolls') way to go.

Hi
My enclosure is custom made to fit to the available space in the lathe.



There is a gap where the original protection and control circuits were located.


The paint was custom mixed to match the original colour.



I also changed the motor and made pulleys to fit a poly-Vee belt to replace the dual V-belts.

Again.... Nicely done.... Out of curiosity, what is the gauge/thickness of the metal you used for the box, and what did it end up weighing. I need to make a box for my CNC and I'm grappling with how thick a metal to use as weight is a problem. Sure, I understand that it is all about the size of the enclosure... Getting a feel for how stiff something is when assembled has never been my forte. I'm also curious if you used a break at all or are your sides all welded together? It looks like you bent the front but I can't really tell about the rest (I'm assuming that if you had the ability to bend anything, you'd like do as much as you could.

MrMetric said:

I gone several routes.... I have built a phase converter using a 3 phase motor and capacitors for tuning. This works well but does consume some power when you are not using shop motors. It also can be a little noisy. I ended up moving the idler outside in a small hutch (dog house type thing), which worked well.

For small motors, I've used the VFD route. You should be aware that this only works for motors that are about 3HP or smaller, though. And you should over-rate your VFD. Finally, not all VFDs will work; look for one that says it can take a single phase input or call the manufacturer. Although it is true that ultimately the three phase is rectified and put onto a high voltage DC bus (from which the three phase is generated), some VFDs sense the input legs and will fault if it doesn't see everything.

The last route I've gone is a Phase Perfect. This is probably your best solution for larger machines or, arguably, CNCs that require a transformer. What does that mean? I'm in North America where my power is 220V. I have a European CNC that is 380V three phase. It has its own custom VFD built into it and choosing the legs that powered the control simply was not possible. I *had* to have a step up transformer. I had difficulty getting the rotary to work well because the control had sensitive lead/lag detection circuitry. I finally went with a Phase Perfect. These are essentially VFDs that are designed specifically for loads to be switched on and off. That means they are intended to act in a way where they can be connected to a load panel and supply the whole shop. They can also work with 10HP motors or more. Sadly, Phase Technology has the patent on them and they really do want to collect the money. You can expect to pay 2K for a setup.

One word of caution. If you choose to use a traditional VFD as a phase converter, DO NOT put heaters or any other interrupter (switch, protection) after the VFD. Simply put, unless the VFD is designed for it (only Phase Perfect, as far as I know), it will *not* tolerate loads being switched off. The VFD acts as the switch and the protection device (through parameter settings). This is why you can't use a large VFD to power a whole shop, switching different loads on and off... You'll kill your VFD if you try that.

Click to expand...

Smiling

Quoting - - "You can expect to pay 2K for a setup." - - - - If only that were true!
I've gotten quotes about every 18 months from those boys (Phase Perfect).
And yes my last quotes are for bigger models (I could go smaller if all I wanted to power were this one machine) but the models that I was considering are both much more than the lathe. (Therefore the question for a 'cheap' way of doing this.)
If I had the spare cash I would be all over that idea but sadly there just aren't the spare funds for that at present.