Alternator

1.What is the speed of a 100 kW, 230-volt, three-phase, four-pole, 60 Hz alternator?A. 450 rpmB. 900 rpmC. 1200 rpmD. 1800 rpm

2. A three-phase star connected AC generator is rated at 2.5 MVA, 11kV, 60Hz. The generator has a negligible resistance and a synchronous reactance 20 ohms per phase. To what value will the terminal voltage rise when full load at 80% pf lagging is switched-off?A. 14.2 kV C. 15.3 kVB. 13.5 kV D. 12.7 kV

3. A 30 MVA, 15 kV three-phase alternator will have a per phase nominal impedance of?A. 7.5 ohmsB. 9 ohmsC. 15 ohmsD. None of these

Transformers

1. Calculate the total magnetic flux in a 60-cycle transformer in which the induces emf per turn of the winding is equal to 2 V.A. 7.50 mWbB. 7.02 mWbC. 7.35 mWbD. 7.42 mWb

2. The low side of a certain welding transformer has 2 turns and delivers 300 A. if the high voltage side has 300 turns, how much current flows through it?A. 10 AB. 12 AC. 20 AD. 15 A

3. Two identical 1-phase transformers connected in open delta will serve a 3-phase motor load of 250 hp, 0.70 pf lagging, 0.90 efficiency. Solve for the minimum size in KVA of each transformer required to serve the load without overloading.A. 150.33B. 170.91C. 160.43D. 185.13

3-Phase Induction Motor

1. The motor speed of a six-pole, 50-cycle induction motor is 960 rpm. Calculate the percent slip?A. 5%B. 2%C. 3%D. 4%

2. What is the speed of an induction motor of si poles if the percent slip is 2.5%?A. 1462 rpmB. 1170 rpmC. 877 rpmD. 1755 rpm

3. A 150 HP, 3-phase, 6-pole, 460 V, 60Hz induction motor draws 195 A line current at full load speed of 1170 rpm and 0.85 pf. Solve for the slip at full load.A. 2.5%B. 3%C. 2.8%D. 2%

Synchronous Motor

1. A 1000 kVA, 11 kV, 3-phase Y-connected synchronous motor has a resistance of 3 ohms and a reactance of 25 ohms per phase. Determine the induce emf when fully loaded at 0.8 pf laggingA. 5521 VB. 5362 VC. 5475 VD. 5582 V