50 Electrical Machines Numerical Practice Problems With Final Answers

50 Electrical Machines numerical practice problems with final answers. PART 1: TRANSFORMERS (1-15) 1.A 2200/220 V transformer has 1000 primary turns. Find secondary turns. 2.A 50 Hz transformer has max flux 0.02 Wb and 500 turns. Find induced EMF. 3.A transformer supplies 10 kW at 0.8 pf. Find apparent power. 4.Copper loss = 500 W, Core loss = 300 W, Output = 10 kW. Find efficiency. 5.A 100 kVA transformer has 2% resistance. Full load copper loss? 6.If frequency increases, what happens to flux? 7.Transformer turns ratio 10:1. Primary voltage 2000 V. Secondary voltage? 8.Voltage regulation = (220200)/200 100 9.Transformer efficiency is max when? 10.A 50 kVA transformer delivers 40 kW at 0.8 pf. Find load percentage. 11.OC test measures? 12.SC test measures? 13.Transformer output 25 kW, input 27 kW. Efficiency? 14.Turns ratio 5:1. If secondary current = 10 A, primary current? 15.If voltage doubles, flux becomes? PART 2: DC MACHINES (16-25) 16.DC generator: P=4, Z=500, =0.02 Wb, N=1500 RPM, A=2. Find EMF. 17.DC motor: V=220 V, Ia=10 A, Ra=1 . Find back EMF. 18.Torque Ia. If flux doubles and current doubles, torque? 19.If load increases, DC shunt motor speed? 20.Armature resistance = 0.5 , current = 20 A. Copper