# Maximum Flux in transformer core

Discussion in 'Homework Help' started by Zaraphrax, Oct 8, 2009.

1. ### Zaraphrax Thread Starter Active Member

Mar 21, 2009
47
3
Say I have a transformer of:

Vp = 230V - Primary Voltage
Vs = 110V - Secondary Voltage

N1 = 400 - Primary Turns
N2 = 191 - Secondary Turns

Ac = 4000 mm^2 = Core cross-sectional area

And I wanted to calculate the maximum flux (in Tesla) when the supply voltage is at 50 Hz and neglecting all losses, would this formula be the one I am after?

(Vp * 10^8)/(4.44FAcBmax) = N

Thanks.

2. ### Zaraphrax Thread Starter Active Member

Mar 21, 2009
47
3
Sorry, I meant Webers not Teslas.

3. ### t_n_k AAC Fanatic!

Mar 6, 2009
5,448
787
If you only require the maximum flux (rather than flux density) you don't need to know the core CSA.

In any case I go back to basics

Vrms = 4.44*f*N*A*Bmax = 4.44*f*N*$\Phi$max

where f is in Hz, A is in m^2 and Bmax is in Tesla

If A is in mm^2 then

Vrms = 4.44x10-6*f*N*A*Bmax = 4.44x10^-6*f*N*$\Phi$max

So whichever you need, re-arrange to give either Bmax or $\Phi$max

I'm not sure where the 10^8 factor comes from in your equation - perhaps it applies to different units.

4. ### t_n_k AAC Fanatic!

Mar 6, 2009
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787
Sorry, the second equation with area A in mm^2 should just be ....

Vrms = 4.44x10-6*f*N*A*Bmax = 4.44*f*N*$\Phi$max

since area is of no relevance in the case of flux $\Phi$

5. ### bensm0 New Member

Nov 10, 2011
1
0
Where has the 4.44 figure come from?

6. ### t_n_k AAC Fanatic!

Mar 6, 2009
5,448
787
It's an approximation for

$\frac{2*\pi}{\sqrt{2}}$