The following data were obtained on a 20 kVA, 50 Hz, 2000/200 V distribution transformer: Draw the approximate equivalent circuit of the transformer referred to the HV and LV sides respectively.
| Voltage (V) |
Current (A) |
Power (W) |
|
| OC test with HV open-circuited | 200 | 4 | 120 |
| SC test with LV short-circuited | 60 | 10 | 300 |
OC test (LV side)
Y_{0} =\frac{4}{200} =2\times 10^{-2} \mho ; G_{i} =\frac{120}{\left(200\right) ^{2} } =0.3\times 10^{-2}\mho
B_{m} =\sqrt{Y_{0} ^{2}-G_{i} ^{2} } =1.98\times 10^{-2} \mho
SC test (HV side)
Z =\frac{60}{10} =6\Omega ; R = \frac{300}{\left(10\right) ^{2} } =3\Omega
X =\sqrt{Z^{2}-Rx^{2} } =5.2\Omega
Transformation ratio,
\frac{N_{H} }{N_{L} } =\frac{2000}{200} =10
Equivalent circuit referred to the HV side:
G_{i} \left(HV\right) = 0.3\times 10^{-2} \times \frac{1}{\left(10\right) ^{2} } =0.3\times 10^{-4} \mho
B_{m} \left(HV\right) =1.98\times 10^{-2} \times \frac{1}{\left(10\right) ^{2} } =1.98\times 10^{-4} \mho
The equivalent circuit is drawn in Fig.3.26(a).
Equivalent circuit referred to the LV side:
R\left(LV\right) =3\times \frac{1}{\left(10\right) ^{2} } =0.03\Omega
X\left(LV\right) =5.2\times \frac{1}{\left(10\right) ^{2} } =0.052\Omega
The equivalent circuit is drawn in Fig.3.26(b).
