3 Phase CNC machinery in 1 Phase shops - FYI

[Reflexx]

This is just a little FYI for those thinking about adding or moving a CNC mill to a 1 Phase (home based) shop.

I'm going thru the 3PH to 1PH issue right now and it's something very serious to think about BEFORE buying a 3PH CNC mill

I've got a Cincinatti Arrow 500 CNC mill (10hp, 20x20x20 travels). In my (industrial unit) shop now it runs great off a 50amp breaker (never tripped, no issues). Well the shop I'm building is in a 1PH area and NO chance the power company will give me 3PH! "Tens of thousand to run a line just for me" they say.

So I'm stuck with single phase. I figure no problem. 10hp mill, add a rotary phase converter for $1,200 and I'm good to go. NOT SO. the 10hp is just the spindle motor, I have to add the axis motors (2-4 hp each) and the total is more like a 16hp machine as far as load (KVA) is concerned. This means that the machine has the potential to pull 64 amps under FULL load. No problem ,bigger rotary phase converter for about $1,800.

For those not familiar with phase converters. They take 1 phase power and convert it to 3 phase. There are three choices for this STATIC, ROTARY and the new DIGITALs. They require more power on single phase to make 3PH, sometimes double.

Static converters are good for "dumb" machinery. Basically lathes, Bridgeport style knee mills, drill presses. In other words, no electronics, relatively slow motors.

Rotary converters actually use a spinning motor to generate 3PH. These are made for bigger machines and provide slightly "cleaner" 3PH power. I thought this is what I need for my CNC mill.

I call up Cincinatti and ask them what it takes to hook up the rotary. The guy said for me to kiss my machine goodbye (all $50, 000 of it!). He said if the phase converter does not deliver BETTER THAN 99% clean & efficient power, that it will slowly destroy the very sensitive electronics and the servo motors ($4,000 each). The rotaries do not! No matter what they tell you. He's seen neumerous machines die because of dirty power.

I thought I was screwed, I HAD to make this machine work off 1ph. So I stared digging and found DIGITAL phase converters. I did a search and only one company makes them. www.Phaseperfect.com (http://www.Phaseperfect.com) so I called the guy up and told him my dilemma. IN a nutshell, these DIGITAL converters are patented and nobody else makes them, they are expensive BUT, he claims, they give you cleaner power that the electric company.

He guarantees that I'll never have any power issues, and the tech stuff seems to back it up. But here's the catch, they're friggin expensive!!!

For my 17hp machine, I need a 20ph unit. It's $4,000!!! and I have to run a 125amp breaker ($50) thru 2/3 romex ($2.50 ft x 60ft) to a 200amp disconnect box & fuses ($150) HOLY CRAP. :eek:

The other bennies are that it's as quiet as a PC and state of the art tech.

All things considered, the other choice is not to move and that's not a choice for me.

The 10hp unit is "only" $2,500, so that's a little more affordable. It's all relative, I would hate to spend $15 to $100,000 on a CNC mill to have it die an expensive death. I guess I have to look at this as insurance.

DISCLAIMER: I'm far from an expert, it's just what i've learned in the last few weeks.

later,

REFLEXX :D

[MC]

You should be running a 30hp unit not a 20hp unit but your using something different than a rotary. When your at 80% your ratings drop significantly so I would talk to tech (from the phase converter comapny). I know I went through the same thing. We are in two buildings and building #2 doesnt have 3 phase but we have a cnc lathe and all our welding/bending equipment in #2 so we needed to look for a 3phase rotary converter. After talking with the techs and americanrotary.com for our little 12hp machine we needed a 25hp rotary. It may be different but we paid $1100 for the converter and it was all AMERICAN made. :)

[70cyclone]

man am I the only one with a full CNC that can run it single phase?
Are you sure you can't just wire it properly for single and take the hit on max hp output???

[fj40guy]

man am I the only one with a full CNC that can run it single phase?
Are you sure you can just wire it properly for single and take the hit on max hp output???

:confused:

So you are running a three phase CNC that only required a single phase? Nothing else, just hooked up two wires and ran it?

If you use a capacitive start (fine for older three phase machines) you can get those three phase motors running... at 60% max power rating. My mill has a 2 hp motor, so this allows it to start rotating. Fine as my power feed motor is single phase. Once the mill is running, no much need to stop and start the motor that often. Not the case will my lathe, so a "rotary convertor" was added for that reason.

The older electronic control was much more sensitive to phase and corrections, newer stuff uses a wide range power supplies. Lots of changes over the years, so the "dirty power will kill CNC controls" needs to be taken with a grain of salt (still adding a power conditioner will help prevent damaging spikes from killing stuff).

As the PhasePerfect stuff... modern electronics & current measurements can allow a pretty clean supply. I had played with this stuff for some time, fine turning harmonics/waveforms for maximum power transfer. My old electric 3phase truck is long since gone, but some photos are still on the net. :flipoff2:

MC -- he is correct with PhasePerfect rating at 20HP. For a rotary convertor (idler motor) you want a 3450rpm motor at least 50% larger... hence a 30hp idler for a 20hp machine)

Suprised no one was a ARMY TECH. Lots of military stuff uses phase convertors. Basically a large ELECTIC motor turning a generator to produce the voltage/frequency needed.

SIMPLE TESTING TOOL: Take your Three Phase (208V) and run two light bulbs in series between the phase. Six bulbs total. You know can visually see when the phases are balanced. Pretty simple, but will help in knowing how things are running. Welders (old school) have a bank of caps to help get the Voltage and Current back in synch for max power transfer.

Tom :usa:

[Reflexx]

gents,

Thanks for the replies. I'm hoping more people will add thier experiences.

Fj, Your right on about the rotary needing to be 30hp, but this one 20hp is ample. Also, the guys at Cincinatti mentioned that they have had several servo motors & control boards go out on machines hooked to rotary PH converters. They could not find any other reasons on those particular machines. This machine is actualy wired for 380 (a British made machine) So I've got a transofrmer on it too. I cannot risk having this machine crap out on me, so like I said. it's $4,000 insurance.

Trust me I'd prefer the $1,200 solution. But none exists.

later,

REFLEXX

PS- for anyone buying a Bridgeport type mill. Take a look a the WEBB brand. They call them "Champ" The one I bought came with a "frequency drive" it works on 3PH or 1PH just by changing wires and it's damn quite.

[Scott@Rockstomper]

Guess I got luckier than I thought with the CNC mill here. The CNC portion runs happily off of 110 single-phase, the only thing that it actually uses three-phase for is the spindle. And that's perfectly happy to run off even a static conveter (I've done it) or a rotary (as it currently has).

I was told, with rotary converters, you don't need to add the horsepower draws of everything, unless it's all starting at exactly the same time. You only have to go by the largest of what you want to run, or the sum of whatever starts at the same time, (whichever is larger) and get a rotary converter rated for 50% over that. Maybe I was told wrong?

[70cyclone]

:confused:

So you are running a three phase CNC that only required a single phase? Nothing else, just hooked up two wires and ran it?

If you use a capacitive start (fine for older three phase machines) you can get those three phase motors running... at 60% max power rating. My mill has a 2 hp motor, so this allows it to start rotating. Fine as my power feed motor is single phase. Once the mill is running, no much need to stop and start the motor that often. Not the case will my lathe, so a "rotary convertor" was added for that reason.

The older electronic control was much more sensitive to phase and corrections, newer stuff uses a wide range power supplies. Lots of changes over the years, so the "dirty power will kill CNC controls" needs to be taken with a grain of salt (still adding a power conditioner will help prevent damaging spikes from killing stuff).

As the PhasePerfect stuff... modern electronics & current measurements can allow a pretty clean supply. I had played with this stuff for some time, fine turning harmonics/waveforms for maximum power transfer. My old electric 3phase truck is long since gone, but some photos are still on the net. :flipoff2:

MC -- he is correct with PhasePerfect rating at 20HP. For a rotary convertor (idler motor) you want a 3450rpm motor at least 50% larger... hence a 30hp idler for a 20hp machine)

Suprised no one was a ARMY TECH. Lots of military stuff uses phase convertors. Basically a large ELECTIC motor turning a generator to produce the voltage/frequency needed.

SIMPLE TESTING TOOL: Take your Three Phase (208V) and run two light bulbs in series between the phase. Six bulbs total. You know can visually see when the phases are balanced. Pretty simple, but will help in knowing how things are running. Welders (old school) have a bank of caps to help get the Voltage and Current back in synch for max power transfer.

Tom :usa:


I hooked 220 single phase to L1 and L3 and ran a jumper from L1 to L2 as we(Milltronics) always did for single phase customers. Since the machine has a programable spindle its no problem.
I have a spare spindle drive that I am going to run single phase on my big manual lathe thats going into my home garage. The nice thing about that is I will have variable motor speed on top of the gearing in the head plus ramp up/down of the spindle. I had the setup on my manual knee mill before I got the CNC and it worked great.

[fj40guy]

I hooked 220 single phase to L1 and L3 and ran a jumper from L1 to L2 as we(Milltronics) always did for single phase customers. Since the machine has a programable spindle its no problem.

Got it. I was thinking a dumb three phase motor. You had a electronic speed control that could accept either single or three phase.

Tom :usa:

[70cyclone]

Got it. I was thinking a dumb three phase motor. You had a electronic speed control that could accept either single or three phase.

Tom :usa:

exactly :D

[86turbodsl]

Why has no one mentioned VFD's?

Split your CNC controls off and run on single phase. They always are single phase.
Run your spindles on a VFD or two.

Go to www.practicalmachinist.com and ask on the VFD forum. Lot's of smart guys there that haven't bought phase perfects.