Hey guys,
I got a problem. I need a single phase transformer. I have (7) 400W MH low bays that I am installing. All of them are wired for 480v, no multitaps. I got 208 in the building. My suppliers tell me the only way to do it, is to use a 3 phase transformer and use it as single phase. They tell me no-one makes a 208-480 Single phase transformer at 1kva or smaller.

Anyone run into this, does someone out there make this, and what if I went with a 240-480 single phase, the lights would have @420 to them. I would think they would still work, or is the 3 phase trans a better way to go.

Thanks
Dnk

What is the amperage draw per fixture? Could you balace the single phase loads in the new panel off of the trans? Stay with a trans. that is 480v primary, and 208v secondary. I'm not sure what size KVA trans. yet till the load is determined.

7 x 400W = 2800W, which is considerably more than 1 kVA. So you appear to be outside of the "1 kVA or smaller" territory you're worried about.

[This message has been edited by SolarPowered (edited 01-20-2005).]

This doesn't make sense. Why are you installing 480 volt lights if you know you don't have 480?
The only reason I can think of is that you got the lights for free or nearly free.

The conversion can be made but it doesn't seem worth it for 7 lights.

If you get a 3-phase transformer, you can spread the lights over three phases.

Get a buck boost trans. 208/240, then another trans. 240/480., or just get new lights.

OK, heres the situation.
Customer of mine has a 100,000sq/ft shop. 30' cielings with 400w MH low bays. (wrong lights to begin with, and I didn't sell them to him)

He is expanding, taking over the building down the street. 23,000sq/ft 16' cielings.About a year ago he started taking the building over and we installed 18 400w low bays in the area he took over. very nice and bright over there for assy. of small parts and some machines. Now he is waiting for the tennant of the new building to leave so he can take the whole thing over. Right now, he took over another small area.

He and his workers always complained about the lighting in the orginal building, like I said 400w low bays in a 30' cieling. It has maybe at best 30 ft/candles at the floor. I talked him into buying 1000w MH high bays, to replace the 400w Low bays and move the 400w low bays to the new building next door.

So in a sense, the 400w low bays are free. Now I have to make these work over there. There is no sense in buying new 400w lights that are 208. I can use the 400w and either buy new ballasts for them or buy a small 480 transformer to power these lights. The latter seems like a better option.

The orginal above post of mine should of said 3kva, not 1kva. I should of reread that and caught it.
Anyhoot, back to the supplier thing. They tell me no-one makes a 3kva or smaller single phase transformers. Yet a 3kva 480V transformers are listed in my reference book, with a load of 6.25a.

I assume someone makes them, maybe my supply house doesn't deal with a manufacturer who does, but I gotta believe someone does.

I take it no-one has done this before, and if so, does anyone know of a manufatcurer who makes one this small.

This is a temp thing. Like I said, when the tennant finally gets his **** completly out, I will have (36) 400w low bays to put up. After we put up (36) new 1000w high bays. Then we can go the route of a larger 3 phase transformer, for all the lights and machines, but for now, these new 7 lights are the only 480 needed. The tennant needs another year to move.

WHEW, any ideas from you guys now.

Thanks for listening.....

I know you may have already considered this, but I would lean toward putting the bigger txfrmr now. It may solve your availability issue as well eliminate the extra work of installing the smaller, if the larger will go in anyway.

I might wiegh the Tranny idea against changineg the cores out of the lights. You have to take 'em down anyway, it'll only take a few minutes each to change out the cores, and slap 'em back up in the new place.
---------------------------------
Then when you go in for real, just start fresh.

[This message has been edited by e57 (edited 01-20-2005).]

DNK:
Sq D 1 phase, 240/480pri-120/240 sec. Mfg # 5S1F (5KVA) Wire it 'backwards' 240sec as your pri; 480pri will be your sec; you should get about 454 volts 'out' with 208 in.

Now that I said that, the xfr is 'book' at $450 W/790 list, so by the time you get this all together, it will be more cost eficient to replace the ballasts. 400MH M/T are $120 at WWG (HIGH), and like e57 said 'ya took 'em down anyway"

John

I really don't like the idea of stepping voltage up to 480V just for a few light fixtures. I undstand how you feel though. You have to pipe them in, pull wire, set boxes, provide a way of turning them on and off, probably add a breaker in a panel somewhere, and hang the fixtures. The question is, can you buy a 3 phase 208/480 Volt transformer for less than the 7 balasts? I don't know..... You still have to buy the transformer, install it, pipe into it and out of it.....I wouldn't. I'd buy some ballasts.

That 208V ain't broke, don't go fixin' it,
Doc

Hotline,
You must have pressed enter before I did. You stoled my thunder.

Doc

New ballasts=New fixtures
Transformer=Old Fixtures
I'd do the ballasts, I think.

[This message has been edited by electure (edited 01-20-2005).]

Thanks to all for your thoughts, I'll let you know how I made out.

Dnk

HotLine1: wouldn't that be 416 volts out?

Why not wire the 120/240 side as 120 and run it from a 120 volt L-N connection?

 
Consider a drytype with hiside taps. Using the lowest (-5%) FCBN tap, a ratio of 480:240x0.9, 208V on the secondary will produce ~437V on the primary.
www.acmepowerdist.com/pdf/Page%209.pdf
www.acmepowerdist.com/pdf/Page%2055-63.pdf
Connection Diagram 3 — PRIMARY: 240 X 480 SECONDARY: 120/240 TAPS: 2, 2½% ANFC, 2, 2½% BNFC

[There are 208∆—480Y/277 transformers available, but they start at 15kVA. ]www.acmepowerdist.com/pdf/Page%2014.pdf]




[This message has been edited by Bjarney (edited 01-22-2005).]

 
To save some transformer capacity, it may be possible to obtain a 208—120/240V 1ø drytype, connected in a split autotransformer configuration.
www.acmepowerdist.com/pdf/Page%2055-63.pdf
PRIMARY: 208 SECONDARY: 120/240 TAPS: 2, 5% BNFC

480V discharge fixtures should operate acceptably down to about 440V, although cold weather or motor starts on the 208V system my complicate this. If nonimal 208V runs low, moving the transformer connection from H4 to H3 will increase output voltage. {Its normal for 150°C-rise drytypes to run very hot—they should always be mounted in an area with adequate ventilation and clearances as labeled.}






[This message has been edited by Bjarney (edited 01-22-2005).]

Thanks Bjarney, I had no idea you could do that to that type transformer.

I appreciate your input on this dilema I am having. The prices I got from suppliers for a 3kva is about the same price as a 15 or 30kva 3phase transformer.

However, I found a reconditioned GE 120-460 single phase 3 kva from Midwest for $100.

http://www.swgr.com/products/DRYXLO_Inv_GENERAL%20ELECTRIC.asp

They are not there till monday. I am wondering, (it is not listed on their website) whether this is an open core, dry, or encapsulated type. If it is an open core, like I suspect, can I mount this in a Hoffman box?

Seems like the most economical way for now.


Any input on this?