Boost to 600V from 480V

[TLN]

I am planning a project to replace some of our transformers that have been in service for many many years and are starting to show their age with the insulation on the windings going south. We are doing a boost from 480 3-ph to 600 3-ph using a couple of Square D dry type(50S3H) single phase isolation transformers. These transformers are configured using a HV of 480V and a LV of 120V to give us our boost. I am going to go back with the same type and model of transformer. Just wondering if anyone knew of a place with diagrams or info pertaining to the wiring of the windings. I can make a diagram when we do the exchange I suppose, but was wanting more information. Our plant is utilizing a 3 wire open Delta wiring system.

One other thing, these are 50KVA transformers and they do generate bunches of heat. The enclosures are ventilated with a fan on each one. Any suggestions on a better ventilation of the enclosures. The fans are very small and don't seem to make a real difference either way. Just looking for ideas. I am only running a load of around 420A but have the capacity for 600A. I don't plan on adding more load, but if I wanted to, then the heat would definately be a problem.

 

[redtrumpet]

You could specify 80 C rise transformers instead of the standard 150 C rise. However, a proper solution would examine all factors including the electrical room HVAC capacity. Maybe you don't have enough ventilation or cooling in the room to maintain a reasonable ambient temperature.

 

[JohnHamburger]

I have an old Westinghouse pamphlet that describes in detail the calculations and the connections. I also found a diagram in the Square D technical Library (

http://www.squared.com)

under Transformers (Dry Type Transformer Application Guide). Both of the sources indicate that you can expect to get 433 kVA out of the transformer bank or 520 amperes. I agree with redtrumpet concerning the temperature of the electrical room that you have them in.

 

[TLN]

The transformer banks are in a conditioned room that is maintained at 70-72 degrees F at all times. Actually I have two sets of transformer banks (4 transformers split across two services) feeding one large building. The banks are about 600 ft apart from one another though.

 

[redtrumpet]

If the rooms are maintained at 72 F, why do you feel the transformers are excessively hot? As you say, they do generate bunches of heat.

 

[busbar]

http://www.federalpacific.com/literature/drytrans/FPTS-RTB-0701.pdf

has information on buck/boost appilcations.