A 20 kVA transformer has iron loss 300 W and full-load copper loss 500 W. It operates at 75% full load at power factor 0.8. Determine its efficiency in percent, rounded to the nearest integer.
Physics · Electromagnetic Induction · Mutual Inductance
JEE Mains NEET

Question

A 20 kVA transformer has iron loss 300 W and full-load copper loss 500 W. It operates at 75% full load at power factor 0.8. Determine its efficiency in percent, rounded to the nearest integer.

G1 Physics · Accepted Answer

Output=20×0.75×0.8=12 kW. Copper loss=500×0.75²=281.25 W; total loss=581.25 W. η=12000/(12581.25)=95.38%, which rounds to 95%.