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1. The open-circuit and short-circuit tests results at rated conditions of a single phase 2200/220V 350kVA single phase transformer are as follows: Open Circuit Test: 220 V, 3 A, 400 W . Short Circuit Test: 400V, 159.09A, 40kW a) Calculate the core and winding impedance of transformer referring (14marks) to low voltage side; b) Determine the core loss current and magnetizing currents; and (6marks) c) The maximum efficiency. (10marks) A capacitive load of 250kVA with power factor of 0.8 is connected the transformer. Taking secondary voltage as reference, calculate: d) the voltage regulation; and (5marks) e) the transformer efliciency. (5marks)
4. A 50KW(net), three-phase, 50Hz, four-pole induction motor has a slip frequency of 2Hz at full load. At full-load the stator copper loss is 2.5kW, the iron loss is 1.5kW and the mechanical losses are 0.5kW. Calculate: a) the full-load motor speed: b) the full-load gross mechanical power output; c) the full-load rotor copper loss; d) the full-load net output torque; and e) the full-load efficiency. (4marks) (4marks) (4marks) (4marks) (4marks)