A 200/400-𝑉, 10-𝑘VA , 50 Hz single-phase transformer has at full-load a copper loss of 120 𝑊 . If it has an efficiency of 98 % at full-load unity power factor, the efficiency of the transformer at half load 0.8 power factor lagging will be:
A. 82 %
B. 87 %
C. 92 %
D. 97 %
Answer:D
A 200/400-𝑉, 10-𝑘VA , 50 Hz single-phase transformer has at full-load a copper loss of 120 𝑊 . If it has an efficiency of 98 % at full-load unity power factor, the efficiency of the transformer at half load 0.8 power factor lagging will be:
A. 82 % B. 87 % C. 92 % D. 97 %