Our basic design variables are:

(1) B Core flux density in Tesla

(2) Js OA current density in the
secondary or LV winding in kAmps/ in2

(3)Re Core radius in inches

(4)g HV-LV gap in inches

(5)Rs Mean radius of the secondary or
LV winding in inches

(6)Rp Mean radius of the primary or HV
winding in inches

(7)hs Height of the secondary winding
in inches

(8)ts Thickness (radial build) of the
secondary winding in inches

(9)tp Thickness (radial build) of the
primary winding in inches

(10)Mc Weight of the core steel in
kilo-pounds

(11)Mt Weight of the tank in
kilo-pounds

Note that the last two weights can be
expressed in terms of the othe design variables. However, since some
of the material and labor costs and losses are easily expressed in
terms of them, we find it convenient to include them in the set of
basic design variables.

Their dependence on the other variables
will be expressed in terms of equality constraints. The units chosen
for the above variables are such that their magnitudes are all in the
range of about 1 to 100.

These units are used internally in the
computer optimization program. As far as input and output is
concerned, i.e. what the user deals with, the units are a matter of
familiarity and can differ from the above.

We have not considered the height of
the primary winding a design variable since, in our designs, it is
usually taken to be an inch shorter then the secondary winding.

We express this as hp=αhs, where hp is
the height of the primary winding and α is a fraction ≈0.95. gc
and go are gaps which are fixed and inputted by the user, gc depends
on whether a tertiary or tap winding is present under the LV winding
and go depends on the phase to phase voltages.

H is the window height and T the window
width. X is the maximum stack width ≈2Rc. These are expressible in
terms of the other variables.

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