Question

Two identical 250 kVA, 230/460 V transformers are connected in open delta to supply a balanced 3-$\varphi$ load at 460 V and a power factor of 0.8 lagging. The real power delivered to the load is ______kW.(Assume maximum secondary line current without overloading the transformers).

• A. 346.41

Answer 1

The correct option is A 346.41
The maximum secondary line current without over loading the transformers is,

$I_L=\frac{KVA}{V}=\frac{250\times {10}^3}{460}=543.48A$

$\text{In open delta connection,}$
$P_1=VIcos({30}^{\circ }+\varphi )$
$P_2=VIcos({30}^{\circ }-\varphi )$

$P_{delivered}=P_1+P_2=VI\left[cos\right({30}^{\circ }+\varphi )+cos({30}^{\circ }-\varphi \left)\right]$

$=2VIcos{30}^{o}cos\varphi$

$=\sqrt{3}{V}_L{I}_{L}cos\varphi$

$=\sqrt{3}\times 460\times 543.48\times 0.8$

$P=346.41kW$