Phase Converter on CNCs

[BrandonB]

Hi,

I am new to posting. Been hanging around the site for a couple months now just reading post. I am part owner in a speed shop for about a year now, was in CNC before for 12 years. My question is we have started doing alot of work for area race teams and i am looking at get a VF-1 from a shop that closed down to do stuff on. The only thing is that your shop only has single phase and this is a three phase machine. I wonder if anyone is running a phase converter on there machine and if you see any differences in how the machine runs or if there are thing i need to know about before i make the investment. Anything info would be great.

Thanks
Brandon

[Scanfab]

A buddy here run a Leadwell VNC and all other 3 phase equipment off of a rotary converter, runs off of the two "hots" that come to his house. There is no problems that he has had, run many machines at same time. Just make sure it's rated at least for the max amps of the Haas.. Happy machining!!

[Stewey]

We had a 3 phase generator (diesel) and used to use that- but it was a waste of fuel.
I got a new Aussie-made rotary phase converter- just a 2.5 kW one, and it is terrific. Perfect for the 3HP spindle. It was about $2250 including freight, from memory.

Single-phase 15 amp plug, 240 volts in & 3 phase 415 V.AC out.

I manually set the spindle speed though, with a separate controller- I don't let the software control it.

[GRANDPA]

I'v been on my own in my garage shop for over 30 years. in the mid 70's I decided to get myself a Bridgeport CNC. I bought an Arco phase converter and it worked great. in 1985 I upgraded to a Deckel CNC and got rid of the Bridgeport CNC. only problem I had was on spindle start up, the converter was too small so I bought a new 40 HP model. large enough to handle future upgrades. in 2003 I bought a Hurco VM1 and I ran the Deckel, a manual bridgeport and a surface grinder from the same converter. the only problem I had to watch out for is to not start the spindles at the same time. (too much amps draw). just make sure when you buy a converter that it is built for running CNC, I don't remember why it's been too long. I just retired in July and I am selling my Hurco and Deckel if your interested.


GRANDPA

[whallnut]

As an electrician and industrial electronic technician I would like to warn you of some of the problems with running CNC machines on phase converters.
Most CNC machines have variable speed spindle drives. Many of these drives use regeneration to absorb the braking energy of stopping or reversing the motor. Phase converters only have a return path for single phase energy and can destroy your drive. I have repaired many of them. Although, all of the Haas mills I have seen use resistors to absorb this energy. I'm not sure on their lathes. Another problem I have seen is if the single phase supplies for control power in the machine are connected to the phantom phase, the voltage has a tendency to fluctuate and may cause control issues. HAAS uses a voltage monitor in their control and you may see alarms. Make sure your control power is connected to the true single phase connection.

[tizm]

rotary phase converters work pretty well!! just be careful, if its not big enough your gonna lose some needed HP when takin those deep cuts!

[kvom]

Another problem I have seen is if the single phase supplies for control power in the machine are connected to the phantom phase, the voltage has a tendency to fluctuate and may cause control issues.

You should determine which leg is the "wild leg" and ensure that it is not connected to the control terminal.

An alternative to RPCs are the PhasePerfect boxes; these are pricy but deliver cleaner power.

[metlcutr55]

i run a nardini cnc eng lathe off a rotary phase converter, 8 hp. i bought a 20 hp converter based on recommendations of an electrician that i have extra power for the lathe available, non us motors draw more power on startup? and to have power available if i added another machine. we had to add a buck-boost transformer to get the voltage just right (208 for my non us), and the limiting factor actually turned out to be my small transformer on the pole down the driveway, not enuf juice coming in to spin heavy work in a chuck, or actually to start up quickly, without dimming the lights and shrinking the tv pic in the house. better with collet in and light work.

[Stewey]

Our phase converter, built new in 2008, has a big bank of capacitors, computer-controlled, with which it can switch them on quickly to throw extra current into the 'dead' phase if needed, for smoother starting, and so have totally balanced phases all the time.

Most of the time it's operating under negligible load.

We also run the output of the controller, through a 3phase line filter which came with the router, designed to filter out spikes in the mains supply. After that it goes through a manual frequency adjuster where you control the spindle speed of the router.

I guess it all depends on the age & complexity & price of the phase converter, but it also came with instructions that if you needed to monitor current, or tap a single phase off it, to use a certain pair of wires only- and they tell you which ones.

[elmor fudd]

You would be far better off with a digital inverter as these are much quieter than the rotary type and run really smooth.
Im runnign a full machine shop off a 20HP digital and i never know its there even when the machines are off and im no where near its full capacity.
It was explained to me that if i used a rotary type i could hit problems but those problems wouldnt be an issue if i used the digital type and so far everythings been running smooth

[higgo]

very interesting thread... I have a 94 Hitachi Seiki lathe i bought at auction from the place i used to work at before they went broke. Having thought about getting three phase connected it turns out its just way too expensive (AND i've got 4 mates that work as linesmen!) so... i was thinking of getting a rotary converter or generator. The converter guy assures me that it will run my lathe just fine as i have a large single phase supply, however i can probably buy a generator the same size (about 35 kva i was thinking) secondhand for about half the price of the rotary converter. Has anyone got any ideas on which way i should go? I've been thinking that the power from an a generator might be to dirty to run an 'NC properly?

[Stewey]

My opinion, is you'd quickly get tired of paying for diesel for the generator- 35 kva is a big one. The price difference between the phase converter & the gen-set may be 50%, but the electricity, & wear & taer & servicing of the generator will quickly eat up the difference, and things will go in favour of the more expensive option instead.

It all depends on how long you'll run it for, and how far away it is & how easy it is to turn it off- do you have a remote kill-switch & start switch?

I found I quickly got lazy, and didn't stop it between jobs, when it didn't need to be running, just because I couldn't be bothered spending a minute walking over to stop it, and restarting it.

In time, that's a few $ a day in fuel for no return...