Transformer Equivalent Circuit  Lab Review Sheet
Objectives:
In this lab you will develop the equivalent circuit of a single phase transformer. This will
be accomplished through a short circuit and open circuit test.
Transformer Model:
The equivalent model of a real transformer is as follows:
X1
Vo
Io
R1
Vs
Xc
+

X2
+
Rc
R2

Is
Open Circuit Test:
The open circuit test gives
Rc
and
Xc
.
This test is performed by applying rated voltage to
the low voltage side and leaving the high voltage side open.
Either side may be used but the
voltage is applied to the low voltage side for safety reasons.
With the output side left open in the previous figure and assuming that the shunt
impedances (
Rc
and
Xc
) are much larger than the series impedances (
R1
and
X1
) the equivalent
circuit model reduces to the following diagram.
Vs
Xc
+
Rc

Is
The values of
Rc
and
Xc
can be calculated using the following formulas from the voltage,
current and power measured in this test.
OC
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 Spring '04
 prof
 Electrical Engineering, open circuit test

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