Does anyone have a recommendation for a 5KVA isolation transformer. 208V in 120V out. I have found 120V-240V or 480V but not a lot of luck with 208V.

Thanks
Richard

Richard J. McCarthy
Project Engineer
California Institute of Technology
LIGO Hanford Observatory Ph: (509) 372-8120 Lab 372- 8205
PO Box 159 Fax509) 372-8137
Richland, WA 99352 Email:[email protected]
United States

 

Call Osborne Transformer at (800)229-9410 or see www.osbornetrans.com. They build transformers to order, are very nice to deal with, and I've never had any problems with any of their products.

 

Richard:
Two manufacturers and types for a beginning are: Eaton Cutler/Hammer Type EP S29N11S05N
and
GE Type QMS 9T21B1028G02
May wish to re-verify the catalogue numbers.
Both are 5kVA 208/120.
Hope this helps.
Regards,
Paul Dackermann

 

208 volts is the phase to phase voltage for a three phase 208/120 volt system with 120 volts phase to ground. So if you need an isolation
transformer you could use a 5 kVA 120 in 120 out transformer and connect it phase to neutral instead of phase to phase. This will almost double the primary current so you may have to change the wiring. The reason you have difficulty finding a 208 to 120 transformer is that there is little call for it people would just connect directly to the 120 volt supply.

Any transformer manufacturer can make one for you. But try Acme Electric as they have a lot of choice.

James Bouchard

 

Dear mr.

208V IN for isolation transformer is not recommended as it is not standard . as per your opinion it is correct to have 120-240VAC or 480V.

regards

milind

 

I would disagree with 208 being standard. It all depends on what part of the world you live in. I think it is more common to have multi-tap transformers. I would look for a
210/220/230/240 primary. Again depending on what part of the world I have seen many local vendors that will custom make a transformer of this size. Prices were about the same as
the off the shelf product.

Fred Townsend

 

Try Hammond. I didn't see any standard sizes smaller than 7.5kVA.
Here's the spec I did find.

Part Number: DM007BB
Description: 3ph 7.5kVA 208D-208Y/120 60Hz AL Phase: 3
Frequency: 60 Motor H.P. 5
kVA Rating: 7.5 Type: Drive Isolation

 

Not a very helpful reply if you have 208V power coming in and need to make 120 from it. You should be able to get a transformer from Acme for this. Call your local electrical supply house and they can get it for you. They will even make custom taps if necessary, but I'd bet they have a std one that already does this.

Bob Peterson

 

In an industrial setting 208V is usually the L-L result of a 480 - 120/208V transformation (assuming US) or of a 600 - 120/208V transformation (assuming Canada). If this is a commercial service then you may get 120/208V from the utility. If you don't need to mount this transformer far from the panel you are feeding it from then you could go with a 120 - 120V isolating transformer; you will need a bigger breaker and some bigger wire but this may be quicker/cheaper than the alternative.

Square D make an 'export' transformer that will do the 208/120V transformation for you; see http://ecatalog.squared.com/catalog/html/sections/12/17212002.htm

They also make shielded isolation transformers that will do this for you as well: http://ecatalog.squared.com/catalog/html/sections/12/17212004.htm

If you have a 480V or 600V supply available it be be less costly for you to use a standard transformer.

Another consideration is to use a control transformer. 5KVA is is the upper end but you can get 208 - 120V; see http://ecatalog.squared.com/catalog/html/sections/12/17212014.htm#1011671

You should be able to find equivalents from Cutler-Hammer or Hammond.

--------------------------------------
Danny Scott
Fredericton, N.B.
Canada
[email protected]