Describe briefly the effect of varying excitation upon the armature current and power factor of a 3-$\phi$ synchronous motor when the input power to the motor is kept constant.

Define voltage regulation of a transformer. A 11000/230V, 150 kVA single phase, 50 Hz transformer has cure loss of 1-4 kW and full load cu loss of: 1.6 kW. Determine-

(i) the kVA load for maximum efficiency and value of maximum efficiency at unity power factor.

(ii) the efficiency at half F.L. (full load) and 0-8 power factor (leading).