As can be observed in the Fig. 3, there are two resonance
frequencies in the high frequency transformer. The series
resonance frequency fs is determined by the leakage
inductance (Ld) and the equivalent windings capacitance (Ct)
and the parallel resonance frequency fp witch is defined by
the magnetizing inductance (Lm) and the equivalent windings
capacitance (Ct). The transformer frequency response
depends directly of these resonance frequencies that can be
mathematically expressed by the expressions (1) and (2).
1
s 2. .
d t
f
L C
=
π ⋅
(1)
1
p 2. .
m t
f
L C
=
π ⋅
(2)
The value of the magnetizing inductance is relatively easy
to obtain by analytical ways. However it depends directly of
the reluctance of the magnetic circuit and this parameter is
very sensible to core imperfections and external agents as
ambient temperature.
The other parameters are more difficult to estimate
because they depend of many variables, as geometric
characteristics of the transformer and constructive aspects of
the windings. However, if a same transformer is constructed
with the different winding techniques, the parameters can
vary in a wide range. Therefore, a practical way to obtain the
parameters of a specific transformer must be used.