Question

The HV terminals of a 3-phase bank of three single-phase transformers are connected to a 3-wire, 3-phase 11 kV (line to line) system. The LV terminals are connected to a 3-phase load rated at 1000 kVA and 2200 V line-to-line. When HV is connected in Y and LV in $\Delta$, t he voltage rating of HV winding is ______

• A. 4.1 kV
• B. 2.2 kV
• C. 11 kV
• D. 6.35 kV

Answer 1

The correct option is D 6.35 kV

$\text{11 kV,}Y/\Delta ,\text{2.2 kV, 1000 kVA load}$
$\text{Rating of each transformer}$ $=\frac{1000}{3}=333.3kVA$

$V_{P\Delta }=2.2kV$

$V_{PY}=\frac{11}{\sqrt{3}}=6.35kV$