FLUX DENSITY IN TRANSFORMER CORE

uwed

Joined Mar 16, 2015
64
Generally, the product of winding window and core cross section tells you about the transformer size. It is a transformer with an iron core transferring the power defined by U1 and I1 at a given frequency f. You are free to make the flux density B very small, but the transformer will grow in size, cost and winding losses.
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MrAl

Joined Jun 17, 2014
11,389
Generally, the product of winding window and core cross section tells you about the transformer size. It is a transformer with an iron core transferring the power defined by U1 and I1 at a given frequency f. You are free to make the flux density B very small, but the transformer will grow in size, cost and winding losses.
View attachment 84545
Hi,

When you post a formula like that you should show what every variable stands for, and what dimensions it is in such as inches, meters, etc., Hertz, etc.
 

uwed

Joined Mar 16, 2015
64
Sorry, you are right:

Af, Aw ... core cross section [m2], windings window area [m2]
kw .... windings filling factor --> describes insulation , no dimension, typical values often 0.4..0.7
Srms ... current density in wire [A/m2] (natural convection 1e6...3e6A/m2, forced convection cooling 3e6...5e6A/m2, oil transformer 5e6...7e6A/m2)
B ... peak flux density [T]; has to be below saturation (iron core B<1.7T, nanocristalline B<1T, ferrite B<0.35T, amorpeous core B<1.4T)
U1 ... rms of primary voltage [V]
I1 ... rms of primary current [A]
f ... operating frequency [Hz]

Actually, I put the equation to show that the transformer size is inverse proportional to the flux density.
 
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