Voltage supply for CNC

It depends what voltage is going where. You can run a 208 motor on 240, but it will certainly not run as cool as on

208. Controls can be def'ly be dicey-er. Sometimes you can parse them out to 120 V svc or 220 single phase, so they are not rpc dependent.

The transformer he is talking about is a "buck" or "buck-boost" transformer, and various companies sell them, along with rpc's etc. A 5 or 10 hp capacity transformer was $300 or so from phaseamatic.

It's not a true transformer, with primary and secondaries, but apparently does the job. I have an idea it's something many of us could kluge ourselves, say with an old welding transformer, iffin we knew what we were doin.... :)

I'm surprised these machines don't come with voltage taps. The fadal does, for a wide range of voltages from 190 to 260 in 10 V increments, and then a couple of taps in the 300, 400, and 500 V ranges. wow.....

You should call them up and ask. As redd said, +/- 10%, but you're right, at least the g-d *label* should be right!

I never had a problem running Fanuc controls at the high end of the rated voltage, in fact in my shop 240 vac 3 Ø is always at or above the

240 volt level, usually about 246 vac. Motors tend to run hotter at lower voltages at the same hp output draw. If you really want to drop the voltage just get a buck boost transformer for two legs which would normally be the cheapest way to drop the voltage, but if it were me I would just hook it up like it is.

John

A rule of thumb is + or - 10 % on the voltages.

W.

That's about same as my shops voltage & my OTC's & OTD has been running fine for up to 14 years at that voltage & my Haas.

I'm not an electrician or electrical engineer; but I do just sorta happen to design and build CNC machine tools, so...

The power grid in most of the US is nominally 220VAC; but started stepping up to 230, and then 240, then even slightly higher, about 20 years ago. The power companies can deliver more power through the same old wires if they increase voltage and keep amperage the same. Because few AC circuits are real sensitive, though, you can pretty much treat

220, 230, 240, and even a bit more, as the same basic stuff. 208 is the newer standard, and it's what you'll find in most new installations and buildings. But it's NOT just the voltage that's different. The 220/240 stuff is usually Delta configured. That means there's a big leg (220/240 volts to ground) in the middle of the three phase pattern, and two smaller legs (110/120 to ground) to go along with it. 208 is typically Wye configured, and has no main or "center" leg. In some ways, it's a whole different critter.

CNC controls, or any electronic stuff that runs off a controlled voltage derived from the 3 ph AC, don't often care about the difference between Wye and Delta. All they need is enough voltage to run without overheating. 208 is enough for some 220/240 stuff. For others it's not. But motors, or anything that runs directly from the line power (like coolant pumps, hydraulic pumps, etc.), will definitely want to be the right kind for the type (Y or D) of power you're using. Bad news if they're not.

200 and 400 volt systems are Japanese, and I'm not aware of any safe way to run a machine with those specs except through a transformer. Some folks get away with it. Some are pretty likely to get away with it if they have 208 to start with. But it can be a gamble.

Best bet is to have your electrican and the machinery company's installation tech in your shop at the same time. They can either work it out for themselves, or read each other's drawings, or whatever. That keeps you off the hook if there's a problem, or something that needs to be changed to make it work. It can also prevent nasty surprises and singed eyebrows if you're not totally sure of what you're doing.

KG

...like this retard did:

And then went and tried to blame his own stupidity on someone else.

208 was a real old standard. The electric companies went to 240 centertapped delta to save the cost of another transformer on the pole to generate 115-0-115 volts as well as deliver more power with the same size wires as Kirk said. It was originally done with two pole transformers but then they came up with using one centertapped transformer. But it's NOT just the voltage that's

There are a bunch of ways the electric company can come up with three phase, including corner grounding and open delta. They only need two hv wires coming down the street to give you 3 phase in spite of what many people believe.

Motors run better on the high end of the voltage rating since they draw less amps for the same output shaft HP as proven by all the motors that burn up in a 'brown out'. Where you get into trouble is when the motor core saturates, that is when the iron core cannot increase its flux density with any increase in current or voltage in the windings. When this happens you generate excessive currents in the winding and create heat from resistance losses.

Cheaper motors may not take going over 120% of the nominal voltage rating on the motor. You can though with the380volt 50 cycle motors from europe, run them on 440 volts with no problem since the frequency in the US is 60 cycles and the will increase the reactance ( ac resistance so to speak) so that the motor will not saturate the iron core since the currents will be basically the same. The motor will actually have more available HP shaft output if the mechanical parts of the motor are physically rated to handle it. Also the rpm of the motor will increase by 1/5.

Better get an electrician that is familiar with 3Ø industrial electrical systems. I've seen and had to repair several systems done by licensed electricians that were only experienced in home wiring. Both times they had tied an outlet to the blank space in the electrical panel thinking it was 115 volts which in fact measures about 190 volts to neutral on a center tapped delta system commonly known as a red leg or high-leg, since it was at one time color coded red. About 1993 the NEC changed the color coding of the high leg to orange on any centertapped grounded delta system so it sorta of gets down to just measuring each leg and finding out what you have in the box. Also each electric company had its own system of where the high leg should be installed in the box, usually middle or right side.

John

Standard voltage in Europe is 230V single phase, 400V three phase, ie.

400V phase to phase, 230V phase to neutral, wye connected with neutral point grounded.

Some countries, eg. Italy, used to be 380/220, the UK was 415/240, but the EU has now standardized on 400/230.

Europe is exclusively 50Hz.

Emco is, IIRC, Austrian.

^ ^ ^ ^ LOL^ ^ ^ ^

transformer.

The motor doesn't give one whit about how the power was derived.

The other place you get into trouble with motors is by using unbalanced leg to leg voltages, IIRC your temp rise very quickly goes through the roof after you get past 10% or so voltage inbalance.

Correct.

I did not know the EU went from 380 to 400V.

Thank You, Randy

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I've had two machinery dealers that said they would not install a machine in my shop without the $1500.00 240V to 220V transformer.

My Fanuc just takes the incoming power and makes 300V DC out of it to feed the motor drives. The coolant pump does run directly off the incoming power.

Thank You, Randy

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It happened when they went on the Euro. :)

John

That's cheap for 100KVA. Pick me up a couple. LOL

JC

$75 on craiglist....

yup for your garage shop no problemo...lol--our shop mains are @75kva 1 ph which suports 300 amps appx though they theives call it a 400 amp service....

lol--Well that was for a 35 kva but now its kinda in the way--was never used by me even, I -decided that old welding transformers work great for this sorta thing.

Hint, not much copper in those big ole transformer boxes these days.

If you are really concerned with it all you need is two 24 volt buck boost transformers in two legs of the line. They are a lot less than

1500 bucks. If your machine guys don't know how to hook them up, get someone else that knows. New, those transformers go for under 500 bucks.

John

That's still $1000.00 for two......

Thank You, Randy

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