The company I work for has ordered a large machine from the USA. Its nameplate nomenclature specifies the voltage as 460 3Ø. Our supply voltage is 600 3Ø
My question is; when ordering the transformer I believe what we require is a 600-volt to 480-volt transformer. Based on the fact that I believe 480 volts is a nominal supply voltage in the US and the 460 specified on the "nameplate" is just taking voltage drop into consideration. Am I right in my way of thinking?

I'm fairly confident that I have this right but another electrician I was speaking with figures if the nameplate specifies 460 volts then I should order the transformer to match that voltage.....and for some reason unbeknownst to me the "boss" does not want to contact the manufacturer with this question.

Appreciate any advice

Normal utitliy voltage is 480 volts. Why not order a motor rated for you voltage supply?

Apparently this machine was being used as a demonstrator at trade shows so unfortunately we have to take it as is.

I always see motors with ratings of 110/220 volts on the talley plate.

They are hooked up to 120V or 240V.


I don't think that hooking up the 460V motor to 480V is going to be a problem.

This machine is alot more than just a motor, it consists of many motors,brakes,PLC's,control transformers etc.

Thanks for the replys!

You are correct 480 is one of the US nominal supply voltages.

I would order a 480 transformer without a second thought.

Your within a 5% voltage difference so you definitely have no worries Some machines can start have issues above 10%.Our plants 600v system is at 640v and we have never had any problems.We did call the POCO and found they had run out of taps when we opened the kiosk.All plc's.drives and motors should be happy as long as your within 10%.The machines manual will probably recommend a 5% variance in voltage.Many Canadian built machines get sent to the U.S for the Big Three wired just as you describe.
cheers



[This message has been edited by frank (edited 02-11-2006).]

Quote:
"Our plants 600v system is at 640v and we have never had any problems.We did call the POCO and found they had run out of taps when we opened the kiosk"

Here's a possible problem.

As you know, most devices can "tolerate" plus or minus 10%. And the 460 to 480 is within that (approx. 4%).
But as you noted, what voltage are you actually getting?

We supply nominal 480 volt systems too. But if you are close to one of our substations, where we are allowed to boost the voltage by 5% to compensate for line loss, we are actually supplying closer to 504 volts.

If your utility is giving you 640 instead of 600 volts, you already have about a 6% higher voltage than nominal. Add that to the 4% that your transformer is off and you are pushing your luck.

If nothing else, when you buy your 600/480 volt transformer, see if you can get one with taps so you have a few options.

While I'm at it I thought I would throw another question out there. The machine draws 60 amps, so is a 50KVA Xformer large enough or do you add a "safety factor", and if so how much?
Thanks again guys for the replies.

In Canada and the US motor voltages are always listed differently than the nominal supply voltages from generators and utilities. General purpose transformers also are rated with the nominal supply voltage while dedicated motor/drive isolation transformer are rated with the utilization voltage.

I have never heard a good reason why this difference exists. I do not agree with the idea that it has to do with voltage drop. I just take it as fact and get on with my life. (There is also another rating quirk, in that heating equipment is often rated for higher than nominal voltages)


Supply - Utilization (always 4.17% lower)
120 - 115
208 - 200
240 - 230
480 - 460
600 - 575

NEMA standards ask that motors operate at + or - 10% of the Nameplate voltage.
Transformers have a variety of places where you may connect the wires, to "adjust" the voltage to what you want. It is well within the range of these 'taps' to set them at 460- just ask the guy to do it when he hooks it up.

Is there not a manual or a spec sheet for the machine with a min and max voltage range? Since the machine includes electronic equipment, I would expect such a specification.

A 460V motor is intended to be run on a 480V nominal system. You do not have to worry about +/- operating range, nor do you have to adjust your transformer taps.

There is no major manufacturer of 480V or 600V or 240V three phase motors.

There is no major manufacturer of standard design 60hz power transformers with nominal voltage inputs and utilization voltage outputs (i.e. 600-460).

The "guy" hooking it up is me and whenever I ask him something I get weird looks from other people


No Manual as of yet, just a request fron "the boss" to size a transformer for a 60 amp 460 volt machine.


I do understand this,I was mostly looking for a little reassurance after being questioned by a fellow electrician, always like to make sure I didn't miss something.

It is hard to provide reassurance for something that doesn't exist.

They do not make 480V motors. 460V is not a nominal supply voltage, yet the NEC (US for sure and the CNEC probably) says to make all calculations using nominal voltages.

Don't you have the same problem with 575V motors on a 600V system?

As Long as you do not have more than a 10% voltage variance from nameplate values at the machine you will be fine.
As long as you keep it within that magic number there no noticeable loss in life expectancy or torque reduction.
Also it's better to be a little high rather than low.If you ask me 5% high is perfect since you will be shipping this machine out and you have no control over the customers supply voltage.It's all relative to the machines new home or in this case homes.
cheers

[This message has been edited by frank (edited 02-11-2006).]

Frank,
We are receiving this machine,not shipping it out.

Bigrockk,
What kind of voltage do you normally enjoy at your plant? Is it low or high to begin with?
Or a little from column A, a litle from column B?

I just asked a Leader in machine tool and either a 460v or a 480v xformer will do but if it has a PLC,VFD or Soft Start try to stay at or above 460.What ever you can get cheaper or have in stock would be his main consern.Since you can,check what your 600v supply actualy is and go from there.A Poco owned xformer gives supplies us 640v and they won't repace it because we don't have any problems.
cheers

[This message has been edited by frank (edited 02-11-2006).]

Stay at 480V, that is your nominal supply system voltage, you have no choice.

You will not find a standard 480V motor. You will not find a standard 600->460V transformer nor even a 480->460V one.

460V motors are designed and intended to be used on nominal supply systems of 480V +/- 10% (528 to 432). You do not need to make any accommodations unless you are outside of this range at the motor terminals. All of the motor performance information, including full load current, are based on a nominal supply voltage of 480V.

Look around, I am sure you do not have 600->575V transformers to feed all of the motors in your plant.

I think there might be a little misunderstanding. My original question never was about motors. I fully understand the relationship between motors and supply voltages.
My original question was about a very large machine and the transformer to supply it.
The only reason I posted the question in the first place is because a fellow electrician was questioning me on weather it was correct to order a transformer with a 480-volt secondary when the data plate on the machine specified 460 volts.
I am now assured that a 480-volt secondary is correct.
Thanks for all of your replies!