SinglePhase Transformer Equivalent Circuit
If all flux is in the iron core:
N
1
I
1
N
2
I
2
m
where
is the core
reluctance and
= core length,
A
A = core crosssectional area
I
1
N
2
N
1
I
2
N
1
m
Now define the magnetizing current:
I
m
N
1
m
giving
I
1
N
2
N
1
I
2
I
m
The first term is the ideal transformer load current reflected to the primary side
The primary voltage (still ignoring leakage flux effects and winding resistance) is
e
1
N
1
t
m
d
d
Convert to steady state phasor form:
E
1
j
N
1
m
j
N
1
2
I
m
Let the magnetizing inductance be
L
m
N
1
2
E
1
j
L
m
I
m
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The core losses can be fairly approximated as being proportional to the core flux
squared (at constant frequency), so we may represent these losses with a resistance
Rc in parallel with the magetizing inductance Lm.
The leakage flux is mainly in air paths, so we may approximate its effect by adding
an inductance in series on each side.
Likewise the winding resistances are also
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 Spring '04
 prof
 1%, n1, xm, e1 d N1, ×F N1

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