81
Experiment 8 Transformer Equivalent Circuit
OBJECTIVE
To determine the equivalent circuit parameters of a single phase transformer using the open
and short circuit tests.
DISCUSSION
A real transformer has several inductive and resistive characteristics that can affect performance.
A nonideal transformer is shown below in Figure 81.
Figure 81 Nonideal transformer
A typical equivalent circuit is as follows.
pri
R
sec
R
c
R
pri
X
sec
X
m
X
Figure 82 Typical equivalent circuit of the single phase transformer
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
82
Several parasitic circuit elements exist in a nonideal transformer.
The resistances R
pri
and R
sec
represent the resistance of the copper winding in the primary and secondary coils respectively.
A
small amount of flux travels through the air outside the magnetic core.
The series inductors with
reactances X
pri
and X
sec
are considered leakage inductances and are a result of leakage flux not
linked to the core.
The parallel resistance R
c
represents hysteresis and eddy current losses in the
core.
The parallel inductance X
m
is called the magnetizing reactance and accounts for the finite
permeability of the magnetic core.
In this experiment, the equivalent circuit to be constructed is shown in Figure 83.
eq
R
c
R
eq
X
m
X
Figure 83 Transformer equivalent circuit
Open circuit and short circuit tests can be performed to approximate the parasitic component
values of a transformer.
The open circuit test entails applying power to the low voltage
(secondary) of the transformer while the high voltage (primary) side is open circuit.
The open
circuit test is for measuring the transformer core components (R
c
and X
m
).
The series
components can be neglected in the open circuit test.
This is the end of the preview.
Sign up
to
access the rest of the document.
 Spring '08
 GORUR
 Alternating Current, power supply, equivalent circuit, short circuit test, circuit test

Click to edit the document details