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.
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).]
#62228 - 02/11/0609:54 AMRe: 480 or 460 volt secondary ?
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.
#62229 - 02/11/0610:42 AMRe: 480 or 460 volt secondary ?
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.
#62230 - 02/11/0611:34 AMRe: 480 or 460 volt secondary ?
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)