Ideas for running 3 phase CNC machine on single phase.

I have moved to a new workshop which unfortunately doesn’t have a 3 phase power supply. So I am stuck with 240v single phase at the moment.
I have a 3 phase planer thicknesser, Mortiser and dust extractor which I’m not too concerned about as they all run from a 5hp static phase convertor that I have.

But I am having problems finding a solution for the CNC machine.
I am waiting for a price to put in a 3 phase supply, but I’m expecting it to be prohibitively expensive.

The spindle fitted is 4.5kw 380v 400hz 24,000rpm. (Can this be fun on 240v 3 phase with reduced torque?)
The VFD fitted is 380-480v 3 phase input, 0-380v 3 phase output. 5.5kw (can this run from a phase convertor?)

The options I can think of at the moment are:
Get proper 3 phase installed
Build a rotary convertor (maybe using my static and a large motor?)
Replace the vfd with a 240v in 380v out (I’ve seen one of these but it seems too cheap!)
Replace the vfd with 240 in 240 out and run the spindle on 240v
Replace both vfd and spindle.

Does anyone have any suggestions or pointers?

Thanks for taking the time to read!
Mark.

What fuses has your 240 volts ? Need 20 amps minimum for 4.5kw
And is your motor dual voltage 400-240 volts ??
If so I would swap the VFD with a 240volts single phase unit


Peter

Thanks Peter.
20amps shouldn’t be a problem.
The spindle only says 380v, but I think I read elsewhere on this site that it will run on 240v but with reduced torque at higher speed.
This is the same spindle:
302 Moved

Thanks Mark

Can anyone confirm if the VFD would run from a Rotary Phase Convertor?

Most 3 phase VFD's will run off of a RPC, there may be some small derating if driving difficult loads.What you might look into is a Phase Perfect digital phase converter, they have newer models that have voltage doublers and run off of single phase. You could give them a call to see if the output voltage is adjustable. Alternative would be some combination of a RPC and step up transformer. The Phase Perfects are pricey, but probably more cost effective then pulling in 3 phase power, it all depends on the numbers.

I came across this: YouTube

Thinking that it was interesting, but of not much use to me. It might be useful to you though.

From the video:

"DIY rotary phase converter producing 415 volts 3 phase, from a 240 volt single phase supply.
This converter overcomes a number of issues with old and difficult to run motors, that other converters struggle with."

Thanks for the help and advise so far.
I just thought I would update you with how I'm getting on.

I ran the vfd off a basic rotary convertor.
This worked for a while and we did a couple of jobs on the CNC but then started coming up with an Over Current fault at random times. I’m not sure if this is because the idle motor was under powered

We then bought a 220v in, 380v out 5.5kw Vfd.
This only turned the motor at 2-3 hz and them went pop. We turned the breaker back on and it went bang!
We are trying to discuss this with the seller, but so far, after a week they aren’t being too helpful...

I am now wondering if I can run the original 3 phase 380v in, 3 phase 380v out vfd from a transformer, 240V single phase in 400v single phase out???

I would run 240V 1ph into the rotophase, then take the 240 generated 3ph and pass through a 240:380 (or whatever voltage is optimum for your needs) transformer and feed your CNC with its rated input voltage from the transformer.

rootboy said:

I came across this: YouTube

Thinking that it was interesting, but of not much use to me. It might be useful to you though.

From the video:

"DIY rotary phase converter producing 415 volts 3 phase, from a 240 volt single phase supply.
This converter overcomes a number of issues with old and difficult to run motors, that other converters struggle with."

Click to expand...

i was hoping it was going to be this guys video one of the better ones out there on the delta wye thing and to think this guy is doing this with 240 volt one hot one neutral true single phase not our 240 volt hot hot two phase vary cool how he starts on one for a lower in rush and goes to the other delta wye sorry for going on i just love it when someone makes it work

1yesca said:

i was hoping it was going to be this guys video one of the better ones out there on the delta wye thing and to think this guy is doing this with 240 volt one hot one neutral true single phase not our 240 volt hot hot two phase vary cool how he starts on one for a lower in rush and goes to the other delta wye sorry for going on i just love it when someone makes it work

Click to expand...

I know this is old but it's a common issue with an easy solution.

Most 3 phase motors (within reason)can be run from a single phase 240v circuit via an appropriately derated VFD (at full power).

Derating is necessary because a VFD will have to draw approx 1.73x more single phase power to output the correct 3 phase amps.

E.g. The 34amps a vfd would need to draw to power a 20a 3ph spindle motor would overload a 20a vfd, so a larger one is necessary.

It is worth noting that it's the input rating that needs to be derated. That info is not always provided so VFD suppliers often advise people to simply "double the vfd size for single phase".

Brands like Delta usually state both the input and output rating on their VFD name plate, so use the input one.

This all assumes that you're running a 220v-240v 3ph motor from a 240v 1ph circuit.

For 380v and 460v 3ph motors run on 1ph 240v, there are a number of Chinese VFDs available for motors up to 30hp. Check out this link:

Single Phase 220V to 3-Phase 380V VFD | ATO.com

Based on my personal experience with Chinese 1ph to 3ph VFDs, I'd suggest going at least one size up for CNC spindle motors.

Their 7.5kw 1ph 220v to 3ph 380v should be fine for a 4.5kw 10a-15a motor.

how does one handle the 400 hz issue? I have never checked on the VFD's that I have used on a variety of equipment if they will go up to that frequency. Jim

I would highly suggest finding a way to let the VFD only feed the spindle motors and find a way to get straight from the panel ( L1 and L2) power for the control circuit/computer ( computers love UPS power with isolation transformers). If your Motors are inverter rated that there is a permanent solution with no detractors.