building a test station/traning station

[pdelno]

hey guys whats up.
I am taking a old panel that we have laing around and making a test station. I will be running it with 480 3 phase. There is a step down transformer in it that take 480 to 120 (some one removed the fuses from it so i have to add them back to the primary side). the formula that i have for this is ((KVA*1000)/(E*1.73))*1.25
this is a .85 kva transformer feed from 2 legs of the 480 and i get 1.28 amps now this seem a little low. is this right or is my formula wrong.

 

[bradal]

Well, more importantly, so what if your getting 1.28 Amps, what are you loading it with. Of course you will only get 1.28 Amps with the appropriate load. You need to load the secondary with a resistive load and measure current to find total power so that W will actually equal VA. I would think, but then I am not the best at that stuff.

 

[rsdoran]

It is single phase you are working with so in this case it is KVA times 1000 divided by voltage.
.85 times 1000 equals 850VA
Primary: 850 divided by 480 equals 1.77 amps, a 2 amp would probably work but I would make it fast blow if possible
Secondary: 850 divided by 120 equals 7 amps approximate.

 

[bradal]

Ahhh, yes, read the post wrong. Thought you were measuring 1.28Amps. So I guess............what he said^^^^^^^^^^^^^^^

 

[pdelno]

ok so sense i am only dealing with 2 of the 3 legs of the transformer i would fig it as single phase right. i guess that is where i went wrong.with you figures i might need a bigger tranformer 7 amps on the Secondary is not going to be enough i think. the panel is going to be a multipurpose panel so i might need some more amps.

 

[bradal]

Not sure where your putting this panel but dont you have a plug-in/receptacle near by. Why not take 120vac straight from a 15amp circuit breaker in you building if your looking to get 120volts.

 

[pdelno]

the panel is on wheels and the transformer was in there already.
it is turning out to be a good learning tool