Complex Imaginary Auto Transformer problem

kduff70 · Mar 31, 2014

Hello Im new to the engineering board and I wanted to know if anybody could help me with this problem?

I have a 20 kva auto transformer with a 300v step up to a 600v and the question want to find the turn ratio.

Can someone tell me when does the equation V1/V2 = 1/(1+n1/n2) this seem to be the equation used but how can this be and where does this equation come from I can't seem to find this in any of my auto transformer section of my power books

any help with this would be a great help to me

thank you

kduff70

Bruno · Mar 31, 2014

Kduff,

I have the CI book. Which problem is it? I'll see if I can help.

Bruno

Dexman PE PMP · Mar 31, 2014

Sorry, my mind went somewhere else with that thread title...

Bruno · Mar 31, 2014

In that case, I'll just say I look at autotransformer calculations in a way analagous to impedance divider circuits: V1/V2= 1/(1+n1/n2) = n2/(n1+n2) (V1=VLow and V2=VHigh). That said, a step-up uses the voltage drops across both windings to step the voltage up from VLow (i.e., V1) which is across the N2 windings, to the drop across both windings VHigh (i.e., V2) which is the drop across both N1 and N2.

This makes sense to me but may have muddied the waters for you so let me know if this has helped.

Bruno