Engineering Principles, Electrical Networks Assignment

Engineering Principles, Electrical Networks - Assignment ExampleQuestion 11.1 Calculate line and phase currents?Given3 x 80 resistors star connected415 v three phase supply50 Hz frequencyIL= V/RIL = 415 / 80IL = 5.18 AIn a star connected pervert IL = IphIph = 5.18 A1.2 Total power dissipated by load?P = 3 x VL x IL x Cos Taking index number Factor (Cos ) as 0.85, P will beP = 3 x 415 x 5.18 x 0.85P = 3164.88 tungsten1.3 The power dissipated if, due to fault, one phase of the load went open Circuit?P = 2 x VL/3 x IL cos P = 2 x 414/3 x 5.18 x 0.85P = 2109.92 WattQuestion 2GivenDelta connected loadPower Factor 0.8 laggingP = 4080 Watt425 V supply50 Hz frequency2.1 Calculate safeguard and reactance of each phase?In Delta Connected load Vph = VLThisP = 3 x VL x IL x Cos 4080 = 3 x425 x IL x 0.8Iph = 4080/(3 x425 x IL x 0.8)Iph = 6.93 AR = V*2 / P R = 415*2/4080R = 44.27 Apparent PowerS = P/pfS = 4080 / 0.8S = 5100 WattReactive PowerQ = (S*2 P*2)Q = (5100*2 4080*2)Q = 3060 WattInduc tanceXL = V*2/QXL = 425*2/3060XL = 59.02 2.1 Calculate Line current if same load was connected to star?Delta IL = P/VDelta IL = 4080/425Delta IL = 9.6 AIn Star IL = Iph Star IL = 9.6AQuestion 3GivenBalanced 10 kW three phase load415 V three wire supply18 A line current3.1 determine Load Power FactorPower Factor = aline Power/Apparent Power = P/QThisP = V x I WattsP = 415 x 18P = 7470 WattsS (apparent Power) = 10000 WattPF = 7470 / 10000PF = 0.75Question 4GivenStar connected induction motorSupply 415 VFrequency 50 Hz