Question

The iron loss in a 10 kVA transformer is 1 kW and the full load copper losses are 2 kW. The maximum efficiency occurs at a load of

Answer 1

for max efficiency,
Pcu= Pi

max eff occurs at load of = √Pi/Pcu , KVA

√(Pi/2)
10x √1/2......since Pi is already in KVA
= 7.07 KVA

Answer 2

Answer:

7.07 kVA

Explanation:

The iron loss in a 10 kVA transformer is 1 kW and the full load copper losses are 2 kW. The maximum efficiency occurs at a load of

Condition for maximum efficiency is,

Copper loss Pc = Iron loss Pi

Let say maximum efficiency occurs at k times full load  where k < 1

then  (kI)²R = Pi

=>  k²I²R = Pi

=> k²Pc = Pi

=> k²*2 = 1

=> k² = 1/2

=> k = 1/√2

=> k = 0.707

Maximum efficiency occurs at  0.707 * 10  = 7.07 kVA