# transformer,

Discussion in 'Homework Help' started by ninjaman, Oct 21, 2013.

1. ### ninjaman Thread Starter Member

May 18, 2013
306
1
hello I have this problem:

1. a 3300/250v, 50Hz,1pH transformer has a core of effective cross sectional area of
13000m^2 and a low voltage winding of 80 turns.
Determine:
the number of turns on the high voltage windings
a, 250v / 3300v = 0.075 80 / 0.075 = 1066.6 turns

the maximum flux density of the core

b, 13000mm^2 / 1000,000 = 0.013m^2

3300/4.44*50*1066.6*0.013 = 1.072T

I was told this was wrong, though I cant find what is wrong. I have a guess that maybe the 0.013m^2 may be wrong but im not to sure. or the method for finding the high voltage windings

any help would be appreciated
thanks
simon

2. ### t_n_k AAC Fanatic!

Mar 6, 2009
5,448
783
Your primary turns calculation is the source of the error.

3. ### tubeguy Well-Known Member

Nov 3, 2012
1,157
197
+1 You have a rounding error.
Try solving by cross-multiplying.

4. ### Dodgydave AAC Fanatic!

Jun 22, 2012
5,159
772
ratio of voltages are 3300V/250V = 13.2:1

low voltage turns =80, so high voltage turns = 80x 13.2= 1056 turns

5. ### ninjaman Thread Starter Member

May 18, 2013
306
1
hey thanks a lot everyone for your help
I looked at a few formulas and found that answer

I used np = vp*ns/vs 3300*80/250 = 1056

I then got 1.0828T for maximum flux density by using

3300/4.44*50*1056*0.013

actually im not sure about that last part and cant figure it out properly.

13000mm^2, is that 0.013m^2, I don't know if that's right?

6. ### ninjaman Thread Starter Member

May 18, 2013
306
1
hello

could I get some help, with this, im not sure if im right

13000mm^2 is that 0.013m^2

I don't know if that's correct?

cheers

simon