need help on transformer

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clayton

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ok ive got two questions,

we've got new machines from germany.
one needs 240v three phase with neutral and equipment ground,

the second requires single phase 240v with neutral, and e g this is one leg of 240 and a neutral, 2 wire,

the question is ,what kind of transformer or transformers do i need to go from 480 three phase(star) to get these combinations.


i think the first one i know, just a three phase 480 to 240 Y secondary center tapped for the neutral, but if im wrong please let me know.
and im lost on the second because i think they need 240 between the neurtral and the hot leg.?

any help would be appreciated thank you.
 
Re: need help on transformer

ok i also have available as a power source a 240v single phase (like american style i guess) with the 2legs of 240, perhaps i could use a single phase transformer and tie the secondary two ground ? but im not sure how to get a neutral (grounded conductor) out of that senario?

thanks, clay.
 
Re: need help on transformer

clayton -

<snip>one needs 240v three phase with neutral and equipment ground, <snip>

<snip>i think the first one i know, just a three phase 480 to 240 Y secondary center tapped for the neutral<snip>

I don't know what a "240 Y" is. If you meant 480 pri, 120/240 Delta sec, I think you are okay.

<snip>the second requires single phase 240v with neutral, and e g this is one leg of 240 and a neutral, 2 wire, <snip>

This sounds like a single phase 480/240 transformer. Just ground one end of the 240. If there is a center tap on the 240 windinf just ignore it.

From your post, it sounds like there is a 3 phase, 240V input to run the motors and a 1 phase 240V for the controls.

Not enough information to give you any better help.

carl

My appologies. I didn't see your third post before I replied. And now I really don't understand. I suspect my suggestions don't apply.

carl (again)

[ January 07, 2005, 01:37 PM: Message edited by: coulter ]
 
Re: need help on transformer

one needs 240v three phase with neutral and equipment ground.
Click to expand...
A 240y is 240y/138.7v. The closest standard transformer is a drive isolation transformer which should be available with a 230y/133 secondary.
They usually con with (1)5% FCAN and (1) 5% FCBN tap. I you had a 480v pri. and had 480v using the -5% tap would give you a 5% hogher voltage on the secondary or 241.5y/139.6v secondary.
Drive transformer are common everyday transformers but have additional features directed toward drive applications.
Also
the second requires single phase 240v with neutral, and e g this is one leg of 240 and a neutral, 2 wire
Click to expand...
Again, if this is to be single phase, you refer to 2w but also say that there is to be a neutral. And, one leg of what? Are you looking for 1ph/3w?
If a line to neutral voltage is important you did not specify what it should be.
 
Re: need help on transformer

lets see, these machines need 240v measured between a phase and the neutral. lve been looking them over and their power supplies for the controls have a range from 100v to 230v i assume is nominal. so what im wondering is

will a transformer 3 phase 480 to 240v with the secondary a wye, give me a 4 wire with ground (so 3 hot wires, 1 neutral and 1 eq.gnd.)

that i guess is my question,

i really appreciate you guys answering the first posts. thanks clay.
 
Re: need help on transformer

im doing more and more research,
appears i cant get a wye transformer to do what i want right.

so if ive got a delta transformer three phase
is there a way that i can get 3 phases of 240 and a neutral? plus an equipment ground?, what would the connections be??

as you can tell im not very up on tranformer,connections of this sort.

would you ground one leg(corner) of the delta? and wouldnt that give you a high leg????

Helpppp :) :confused:
 
Re: need help on transformer

Your recent post indicates that you need 3 phase with 240 volts phase to neutral, and it sounds like all three phases must read 240 to neutral. Is that correct? If so, I don't think any of the standard transformers in the US will help. If you have a 240 delta transformer and ground one corner, you have 2 phases at 240 volts to ground, and 1 at 0 volts to ground or neutral. You do however have 240 volts between all 3 phases. Can you tell if you need all three phases to read 240 to neutral or not?
Jim T
 
Re: need help on transformer

jtester, no i only need one out of the three to read 240v to neutral.

ive got a 480v to 240v 3phase transformer wye to delta.

if i corner ground it will i be able to run the 3phase motors off of the three phases? or will the high leg thing hurt me there? also what will that do as far as my return path? on the ground?? meaning my equipment ground??

[ January 07, 2005, 02:42 PM: Message edited by: clayton ]
 
Re: need help on transformer

Clayton
You don't have a high leg, that term is usually reserved for a 120/240 3 phase 4 wire delta. What you will have is a corner grounded delta.
That should have no effect on normal three phase motors. We corner ground 480 volt systems in certain applications, and the motors can't tell the difference. The gear must be rated for 600 volts in the 480 volt example. You must be sure all of your equipment is rated for 240 to ground.
You would run your ground wire with the phase and neutral conductors just like any other circuit, and ground equipment in the same way.
Jim T
 
Re: need help on transformer

It seems as if we are trying to guess as to what you want. Please simply advise what system voltage that is available at the facility, 480v delta, 480y/277, 240v delta, 208y/120 etc. Then advise information on the nameplate of the equipment or as is provided to you be the equipment manufacturer. Otherwise we are just going in circles.
these machines need 240v measured between a phase and the neutral
Click to expand...
if so we are to assume that this is a 3ph wye with 240v to neutral which is 415v L-L or a 415y/240.
To be honest, this is not something to mess around with. Because your question appears to be vague and inconsistant there is a better good possibility we may provide you with an answer that may answer the question as you have presented to us but may be incorrect and dangerous when applied. If you are not familiar with the existing distribution system and can not identify be specific with regard to the voltage need for the equipment it is of my opinion that you consult a person who is qualified to review the facility and equipment in question.
 
Re: need help on transformer

what i have availableis 480 wye (facility bussplug)

what i will go to is 240v

i think i will use is a 480v wye to delta transformer to arive at the 240v L-L 3phase
and what i am really trying to deduce is whether
i can ground one leg of the 240v L-L delta transformer to get a 240v neutral for the controls and still be able to run the motors on 3phase 240v. hope this helps a bit temp.
 
Re: need help on transformer

If you need a three-phase 240 volt supply, with a neutral and a ground - Go to a transformer supplier and order a 480 Delta to 240 Wye transformer - Yes, this is not standard, but Manuf's. can build what ever you need, provided you can handle the lead-time. You would solidly or Resistance ground the neutral of the Wye, unless there is a need to float the neutral. Line Power and Pemco are two companies that make custom transformers - not a problem. On the Single phase unit, just buy a 480-240 transformer and ground one leg of the 240 secondary.

[ January 07, 2005, 04:16 PM: Message edited by: jcormack ]
 
Re: need help on transformer

thanks everyone for your input.
ill get back to you all on the outcome.
meanwhile have a great weekend
clay.
 
Re: need help on transformer

I know I am late in this discussion, but for future information.

Drive isolation transformers are listed with primary and secondary voltages at utilization levels not at supply levels. The typical US transformer primaries are: 230, 460, and 575. And the typical secondaries are: 230, 230Y/133, 460, 460Y/266, 575, and 575Y/332.
 
Re: need help on transformer

If you are looking for 120 control voltage.Just install a small 250 down to 120 control transformer.
You will now have 2 transformers.
If you contact any transformer company they will ask for your load and nameplate ratings.They are real helpful.
Good Luck
 
Re: need help on transformer

Jim,
Yes, that's what I suggested in a previous post and also suggested that if you had a 480v source by using the 5%FCBN primary tap that is commonly available on an MD transformer you could correct thatsecondary 230v to be a tad more than 240v.
Dave
 
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