# Homework Help: Single phaze transformer

1. Sep 4, 2011

### dislect

hi guys,
this is a question from an exam about a single phaze transformer and it goes like this, im sorry for the bad translation in some parts i couldnt find the correct terms:
A single phaze transformer is given with nominal data of - 10k/0/4 kV/kV , 100kVA
A short circuit experiement was done when the low side of the voltage is shorted and the other side (higher side of the voltage) is fed with 500V. The following results came: I=10A , P=1kW

A. what will be the electric current flow and power in the short circuit experiement if the higer side of the voltafe was fed with 400V?
B. we short the higher side of the voltage and feed the transformer on the lower side of the voltage. what should be the feeding voltage in this case to the power will be 1kW? what will be the current?

I gave it a try but it dosent look too succefull could you help me out please?

Last edited: Sep 4, 2011
2. Sep 4, 2011

### Staff: Mentor

Re: single phaze transistor

Can you edit the subject line, and change "transistor" to "transformer"?

Is this a 10kV to 4kV transformer?

3. Sep 5, 2011

### dislect

Re: single phaze transistor

i tried editing the title right after i posted it and couldnt change it

its 10k to 0.4k

4. Sep 5, 2011

### Staff: Mentor

Re: single phaze transistor

I think you will need to show your calculations for the s/c test using 500v, before anyone can say whether you are doing something wrong.

A useful equation is: $P=V.I.cos\phi$

Last edited: Sep 5, 2011
5. Sep 5, 2011

6. Sep 7, 2011

### Staff: Mentor

Re: single phaze transistor

You have Zk=Vk/Ik = 1000 ohms
Why isn't it 500v / 10 Amp?

Where did you find the equation: V=V(1-kLuk.cos(phi - uL))
and, more to the point, do you actually use it?

I can't discern some of your subscripts. What does the subscript "k" stand for?