Complex Imaginary Volume 3 problem 6

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saw

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Hello there,

I don't understand problem 6 in volume 3 of Complex Imaginary. Why s = vI and not S = (sqr root of 3)xVxI? The book says because of delta and Y connection but we consider 3 phase system which it should be the same in delta and Y. I appreciate your comments. Thanks

 
Please post the exact problem. My volume 3, problem 6 appears to be different from the one you're asking about. Thanks.

 
Hi KatyLied,

Sorry for late respond. I was gone for a while and just checked the website. Here is the problem 6: A delta-wye transformer is rated for 34.5kv/480v, 125A primary current(L-L). What is the transformer's power rating(KVA) and the secondary current. The book asnwer is:

S=VI=(34.58kv(X(125A)= 4300KVA

I= S/V=4300/480=8960

The answer is wrong. the formula should be S=sqrt3xVxI

 
Mystery solved and you are correct. as I recall their formula is applicable to single phase and not three. I think you have an earlier version or Complex Imaginary. In my version that problem is number 80 in Vol. 3. In my version they do apply square root 3 correctly.

 

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