A 1, 10 kVA, 2400=240 V, 60 Hz distribution transformer has the following characteristics: Core loss at full voltage = 100 W Copper loss at

A 1φ, 10 kVA, 2400=240 V, 60 Hz distribution transformer has the following characteristics:

Core loss at full voltage = 100 W

Copper loss at half load = 60 W

(a) Determine the efficiency of the transformer when it delivers full load at 0.8 power factor lagging.

(b) Determine the per-unit rating at which the transformer efficiency is a maximum. Determine this efficiency if the load power factor is 0.9.

(c) The transformer has the following load cycle:

No load for 6 hours

70% full load for 10 hours at 0.8 PF

90% full load for 8 hours at 0.9 PF

Determine the all-day efficiency of the transformer.