POWER TRANSFORMER DESIGN VARIABLES BASICS


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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