[Amps] Transformmer design

[Will Matney]

Here is the quotes from the Howard Sams book, "Practical Transformer 
Design" written by Eric Lowden.
Quote;
"Although there are many equations associated with transformer design, 
all of them fundamental, there are two in particular which are usually 
considered as the basic design equations."
"The first one, which we have already met, is sometimes referred to as 
the voltage equation, and the second is the power capability equation. 
They are, respectively,"

"V=4FfaNB X 10 to the neg 8th

V is the voltage across the considered winding in volts RMS
F is the form factor
f is the frequency in hertz
a is the core cross-section area
N is the number of turns on the considered winding.
B is the flux density in maxwells per unti area.

and;

P=0.707JfWaB X 10 to the neg 8th

J is the current density of the transformer in amperes per square 
centimeter ( X6.45 for sq in)
f is the frequency in hertz
W is the area of the core window in square centimeters (X 6.45 for sq in)
a is the cross-sectional area of the core in square centimeters.
B is the flux density in Gauss (Maxwells for square centimeter or X 6.45 
for sq in)"