Banking three single phase transformers..............?i need a little help with my homework. if you bank three single phase dual voltage transformers in a delta connection for the primary and do the same for the secondary, do the kva of primary add together or do the kva stay the same because it is connected in delta. it's a 2:1 480v - 240v each transformer is... |
Your question is a little bit confusing to me but I am going to take a stab at it with what I think you are asking.
If you connect three compatible 5 kva transformers (Delta, Y or single phase) in parallel then their combined total volt amp capabilities become 15 kva. Of course the primary voltages stays the same as the source voltage and the secondary voltages stays the same as they were for a single transformer but the primary and secondary current capabilities triple. Thus the kva rating increases from 5 kva to 15 kva.
It may seem like you are able to generate power by paralleling transformers but you are only adding to the power handling capabilities of the transformers. Any additional power consumed will be determined by the load and furnished by the source generator.
From the output terminals of the paralleled transformers on to the load any formula that was valid for a single transformer is still valid for the three in parallel.
Delta connection it's mean you give 480 V 3 phase, and output 240 V 3 phase.
So the total KVA in delta is 5 KVA and the formula like you said.
Pa = I (current) x Volt x 1.73 (three phase) x cos Q (Cos Phi).
With 3-5KVA transformers connected inbank, your total capacity is 15Kva.To find the line current:
Kva =1.732[V](I)/1000.
Line current, I =KVA{1000]/1.732{V)
I= 15[1000]/480*1.732
I = 18.042, volts at primary.
