Question

A 1500 kVA, 6.6/1.1 kV, 3-$\varphi$ delta-star connection transformer has the following test data,
when low voltage side is short circuited:
300 V, 30 kW, 131.2 A
the per phase reactance referred to delta side is ________$\Omega$.

• A. 3.55

Answer 1

The correct option is A 3.55
$\text{Turn ratio for the two winding,}$

$=\frac{6.6}{\frac{1.1}{\sqrt{3}}}=\frac{6\sqrt{3}}{1}$

$\text{Phase voltage = 300 V}$

$\text{Phase current =}\frac{131.2}{\sqrt{3}}=75.75\text{A}$

$\text{Power dissipated per phase,}$

$=\frac{30}{3}=10kW$

$(75.75{)}^2{R}_{c1}=10\times {10}^3$

$R_{c1}=1.743\Omega$

$\frac{300}{\sqrt{R_{c1}^2+X_{c1}^2}}=75.75$

$\sqrt{R_{c1}^2+X_{c1}^2}$ = 3.96

$X_{c1}=3.556\Omega$