transformer for cnc question

I have a cnc lathe that requires 460v it's a 6kw rated machine 3 phase , my question is I have a transformer here I could use but is a 460 primary to 230 secondary .
From what I can understand some people are saying it can be wired up to work if I connect the 230v 3phase to the output wye side and use the primary delta side for my 460V .
Another question is an isolation transformer a better choice for cnc or is a auto transformer ok as well

Yes it will work, but the 460 volt will be more like 440, I would never use a auto transformer for a step down but they will work for a step up, but they are not the best thing to use and may not be to code...Phil

coyote06 said:

I have a cnc lathe that requires 460v it's a 6kw rated machine 3 phase , my question is I have a transformer here I could use but is a 460 primary to 230 secondary .
From what I can understand some people are saying it can be wired up to work if I connect the 230v 3phase to the output wye side and use the primary delta side for my 460V .
Another question is an isolation transformer a better choice for cnc or is a auto transformer ok as well

Click to expand...

Delta supply into Wye windings? Meahhh... It can be made to work, yes.

Even so, I'd want a 12 KVA or so transformer to do a 6 KVA load with, though. You don't just have to RUN that machine. You also have to be able to START its main load(s), and not just the one-time, but "cycle-wise".

Autotransformers? They CAN make decent economic sense ... up to about 20% - 30% change, buck OR boost. Above that - and at 1:2 you are waaay above it - you are usually better served with full-isolation economically as well as "technically".

That's partly because in larger capacity, full-isolation are more widely used, more common as take-outs from user/business changes, ergo less costly, bought used-but-good.

Example?

There's a 15 KVA 2XX:4XX R.E. Uptegraf Delta-Delta sitting on my lower driveway awaiting a trailer ride to the recycler as would do yah.

But.. even "locally".. as the all-Copper, plus "Eliptical Coil" top-end high-longevity model, no one wants to pay the freight or even haul nearly 400 lbs Avoir!

This one came out of McKean, about a 1,000 mile go-fetch for an under $200 purchase price, but.. I was also picking-up a nice B&S surface plate from McKean... and 5 Reliance RPM III Dee Cee motors from another outfit a few miles away, so..

Since deciding to re-motor wherever I could not simply re-strap rather than deal with 600 Volt-Class, I've had no takers on giving it away!

Similar deals will be "out there" in Canada. They just might be at rather a bit of distance from the Maritimes...

BFD.

Find one that fits the need PROPERLY. "At least" one set of "adjusting taps" is good. More is better. Then go-fetch or pay the freight. Run well and prosper with minimal kludge, reduced risk of marginal rations to the more important CNC rig.

Reduced inefficiency over looong years will pay-off if yah "do it right" and can go "JFDI", worry-free, as to earning a crust with the machine.

Not as if you have to dig-deep into the beer, burger, and band-aids budget every week, is it?

2CW

Well after close examination the transformer I have is the wrong one it's actually 380v/220 can anyone tell me the best transformer to get , I understand I need a 15kva the tag on the machine says 460v 6kw 60hz I'm assuming a 230v step up isolation to 480v?

coyote06 said:

Well after close examination the transformer I have is the wrong one it's actually 380v/220 can anyone tell me the best transformer to get , I understand I need a 15kva the tag on the machine says 460v 6kw 60hz I'm assuming a 230v step up isolation to 480v?

Click to expand...

Not YET sure it IS "the wrong one".

At what operating frequency does the transformer data plate specify those figures?
If @ 50 Hz, it should work OK @ 60 Hz.

Could was it is actually optimized for 55 Hz so it can be "nameplate engineered" for either North America & half of Japan, ELSE the EU and the OTHER half of Japan.

Same again the machine-tool. Where made, by whom, for which market, and what adustments IF ANY, does it have "onboard"?

Give us the makers & their P/N's, "we" can probably look around and find the OEM data to confirm.

And/or one or more other PM'ers HAVE the same goods as you have and already know what works.

I tried it , hooked it up to 236v 3 phase 60hz and had the tap on the 460 which is the highest one , was getting about 275v accross the legs and about 138 from hot to ground.
I realize now that 380v 3 phase gives 220v from neutral to hot hence the 460v delta to wye 380/220v 60hz tag on the transformer , I thought it was 220v .

The lathe is a clausing metosa EL1440CS made by Pinacho for the US , talked to Clausing and they have a record of the sale in 2000 to Canada tag on lathe says 460v 6kw 60hz about 9 amps

coyote06 said:

I tried it , hooked it up to 236v 3 phase 60hz and had the tap on the 460 which is the highest one , was getting about 275v accross the legs and about 138 from hot to ground.
I realize now that 380v 3 phase gives 220v from neutral to hot hence the 460v delta to wye 380/220v 60hz tag on the transformer , I thought it was 220v .

Click to expand...

?? Most of that "does not compute".

Check your test connections. Your recording of what you measured. Your terminology. Or "all of the above".

A) Source is utility-mains 3-P? And - once again, is it Delta or Wye service? If an RPC, it is Delta.

B) "Ground" AKA "PE" or "Protective Earth" is what "PE" says it is. it is not in the "power" equation.

C) Your "Wye" side has an "available" Neutral point, but it is sort of an unemployed "passenger" for the moment.

D) Call things what they are.

You three phases, commonly "A", "B" and "C".

3-Phase happens to share nicely, so uses 3 wires, not six.

Wires are commonly called L0, L1, L2.

IF ... that transformer (which you have not yet ID'ed to us!) really IS a step-up/step-down, not a 1:1 drive isolation unit (as my Delta-Wye, 27 KVA EGS Hevi-Duty assuredly IS)...

THEN ... applying 2XX to the "low" side should produce not less than 380 on the "high" side, any leg to any other leg, 4XX more likely.

ELSE 236 VAC 3-P "leg to leg" in and 275 VAC 3-P "leg to leg", out is part of what "does not compute".

The lathe is a clausing metosa EL1440CS made by Pinacho for the US , talked to Clausing and they have a record of the sale in 2000 to Canada tag on lathe says 460v 6kw 60hz about 9 amps

Click to expand...

Basque-built, then. Decent goods, and usually well-regarded.

Let's sort the power for it...

it was indeed the wrong transformer I had an electrician friend look at it this afternoon and like I mentioned it was a delta wye 460 primary 380 secondary isolation .
I called a custom transformer builder in Ontario and he is building me a 15kva isolation delta wye 235v primary 460v secndary with 5 taps from 440 to 480 hoping to have it in about a week and a half

coyote06 said:

it was indeed the wrong transformer I had an electrician friend look at it this afternoon and like I mentioned it was a delta wye 460 primary 380 secondary isolation .

Click to expand...

Ah, so! NOW it makes sense! A "cousin" to my EGS/Hevi-Duty 2XX Delta to to 2XX Wye.

Unusual in that as it was MEANT for "Drive Isolation", the secondary is not 208 Wye, but (nominally) the same Voltage as the Delta primary. Slight step UP, IOW. That gets me the re-derived Neutral I wanted rather that corner-grounding a Delta (RPC OR Phase-Perfect) converter output.

The only downside is that IF I wanted to utilize one leg to Neutral it would be a tad above 133 VAC rather than 120 VAC, given my mains are also 246 VAC, split-phase "actual" for 123 VAC "real".

IF I needed that nominal 120 VAC for a control transformer, then THAT critter would need adjusting taps. Which is not uncommon.

And I do NOT need it. "Juice" pumps are 1-P, but 208-230 agnostic. No DRO (yet), but similar to the LED worklights I DO have, their PSU is wide-range capable these days.

I called a custom transformer builder in Ontario and he is building me a 15kva isolation delta wye 235v primary 460v secndary with 5 taps from 440 to 480 hoping to have it in about a week and a half

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"Custom?" One can hope it wasn't overly dear!

Hammond is Canadian and well-regarded. We buy a lot of their goods in the "South 48".

AFAIK, what you have needed all along is a stock Hammond (and not-only..) 2:1 step-up SKU with but the basic "10%" adjusting taps. A relatively common one not all that hard to find used-but-good.

Welll. maybe not clear out in the Maritimes? Big land. Small population.

Mostly, you are the better for it, too!

Thermite,
I called Hammond as well as a few other places no one had any step up transformers only step down and nothing from 240 to 460 but lots of 600v step down which is what we have here in Canada for 3 phase, 460/480 seems to be American.
Hammond had a lead time of 4-6 weeks and about $500 more I ended up getting it from EPI in Mississauga ON with a turn around time of 3-5 days so hoping it will be here next Friday so I can play with it next weekend

I see you are in Virginia , my steel supplier is in Sufolk VA, Western Branch Metals great guys to deal with and they have great steel products

coyote06 said:

Thermite,
I called Hammond as well as a few other places no one had any step up transformers only step down ........

Click to expand...

In the US, step down and step up CAN BE the same thing, IF the transformer is "listed for" that usage.

The newer NEC added that prohibition on using in reverse, but left it open that the manufacturer can list it for reverse operation.

IIRC, Hammond has an application note that gives info on it, and most of their units can in fact be used either way.

The issue then is the wye and delta deal. But that is not a biggie, as there is no requirement to use the neutral on the wye side if reversing the transformer, and on the delta side, you can make it "corner grounded", as that has not been prohibited (yet). It is discouraged, but not forbidden.

If you are powering just one machine, "attach" the transformer to the specific machine. That removes it from "NEC" rules and makes the output clearly not a general use "branch circuit", so you are less restricted. You may not even need to ground the output side at all.

coyote06 said:

Thermite,
I called Hammond as well as a few other places no one had any step up transformers only step down and nothing from 240 to 460 but lots of 600v step down which is what we have here in Canada for 3 phase, 460/480 seems to be American.

Click to expand...

Yahbut.. one of my "usual suspects" of used-goods suppliers, NRi, moves goods 'cross-border all the time.

All my nice "600-Volt-Class" Square-D switchgear had been surplused in Canada, for example. NRi made it painless for UPS to drop it on my porch.

Otherwise.. "What JST said".

MOST "dry type" transformers are reversible. There is usually a modest departure from nameplate-nominal Voltage as the more usual practice winds the "power IN" primary closest to the Iron core. "BFD", it's trivial for our typical use.

That said, I LIKE a Wye config, load side.

Modest extra searching time or cost, much nicer to be able to keep all three legs 'bout the same above "real" Earth and @ under 135 VAC, rather than have one leg even "more lethal than usual". Any leg to any other leg is still a bitch, regardless, but there again, I don't "DO" over 250 VAC these days.

"Period".

No compelling reason to do when "NOS" Reliance Duty Master dual-Voltage motors can be had so cheaply, anyway!

Hammond had a lead time of 4-6 weeks and about $500 more

Click to expand...

"MORE?"

IIRC, my EGS/Hevi-Duty 27 KVA Delta -> Wye was only about $400 "outright", and in nearly-new condition even as to paint and cleanliness.

Freight is wot it is. ISTR it net'ted around $700 or so?

Connect the wye side with a neutral conenction, assuming you have it. Then all you have to deal with is marginally reduced voltage output than expected.

There are other nuances and cost cutting measures done in very small transformers that aren't relevant for big ones.

coyote06 said:

Thermite,
I called Hammond as well as a few other places no one had any step up transformers only step down and nothing from 240 to 460 but lots of 600v step down which is what we have here in Canada for 3 phase, 460/480 seems to be American.
Hammond had a lead time of 4-6 weeks and about $500 more I ended up getting it from EPI in Mississauga ON with a turn around time of 3-5 days so hoping it will be here next Friday so I can play with it next weekend

I see you are in Virginia , my steel supplier is in Sufolk VA, Western Branch Metals great guys to deal with and they have great steel products

Click to expand...

im here in ontario, finding a used 600V primary to 230/208V transformer used is like hens teeth. Buying them new is like $1400 around here and easy to get.
I got lucky and when I found my 20HP RPC he had an auto transformer also i bought all for $500. I had put a post up on kijiji and waited a month to find that deal.

So the transformer arrived today but I'm confused to where I should connect the green wire for the ground of the Machine.
The machine requires 3 hots and 1 ground , the output side of the transformer has an XO and 3 hots should I connect to the XO or to the ground.
My understanding is that it should be connected to the XO but will this be right

The grounding conductor from your 230V supply system should connect to the frame ground stud in the transformer case.

The 480V output side common terminal H0 normally, yours sounds like they labeled it XO, needs to be bonded to that same case ground stud.

Then your machine load ground needs to be also connected to that same case ground stud.

For US NEC compliance that ground stud would also need bonding with the building steel, or a metallic water main, just like the building service is.

If you just connected the machine ground to the XO terminal as you asked, the transformer case and coil along with the conduit would not have a fault current return path, and that could become very unhealthy for you, if something were to fault in your wiring.

SAF Ω