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T7 3 ph-ac

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T7 3 ph-ac

  1. 1. ELE101/102 Dept of E&E,MIT Manipal 1 Tutorial 1. A 400V, 3phase supply feeds an unbalanced four-wire star connected load. The branch impedances of the load are ZC = 6∠00 Ω; ZB = 6∠300 Ω and ZA = 5∠450 Ω. Find the line currents and the neutral current. Assume CBA system. Ans: IC = 38.5∠0°A IB = 38.5∠-150°A; IA =46.2∠-285°A IN = 30.6∠56°A
  2. 2. ELE101/102 Dept of E&E,MIT Manipal 2 Tutorial Ans: 104.8∠-120.35V IR = 28.41∠-69°A IY = 29.85∠136.54°A IB =13∠27.60°A 2. A 400V, 3phase supply feeds an unbalanced three wire star connected load. The branch impedances of the load are ZR = (4+j8) Ω; ZY = (3+j4) Ω and ZB = (15+j20) Ω. Find the neutral displacement voltage. Also find the line currents using (i) Neutral displacement method. (ii) Mesh current analysis. Assume RYB phase sequence.
  3. 3. ELE101/102 Dept of E&E,MIT Manipal 3 3. Three similar loads 20∠-450 Ω are connected in delta across a balanced, 3 phase, 400 V ac supply. Determine (i) the line currents (ii) active power (iii) apparent power (iv) power factor and (v) the readings of the 2 wattmeters connected to measure the 3 phase power. Tutorial Ans: 34.64∠15°A, 34.64∠-105°A,34.64∠-225°A 16.97KW 24KW 0.707 3586 W and 13384 W
  4. 4. ELE101/102 Dept of E&E,MIT Manipal 4 4. Two wattmeters are connected to measure the power in a 3 phase circuit read 5 KW and 1 KW, the reading of second wattmeter being obtained after reversing the potential coil of the wattmeter. Calculate the power and power factor. Ans: 4000 W 0.36 Tutorial
  5. 5. ELE101/102 Dept of E&E,MIT Manipal 5 5. Three loads ZR = 10∠00 Ω; ZY = 15∠-300 Ω and ZB = 20∠450 are connected in star across a balanced, 3 phase, 400 V, RYB supply. Determine the readings of the 2 wattmeters connected to measure the 3 phase power, if the current coils of the wattmeters are inserted in the lines R and Y. Tutorial Ans: WR = 2907.2 W WY = 7489.5 W
  6. 6. ELE101/102 Dept of E&E,MIT Manipal 5 5. Three loads ZR = 10∠00 Ω; ZY = 15∠-300 Ω and ZB = 20∠450 are connected in star across a balanced, 3 phase, 400 V, RYB supply. Determine the readings of the 2 wattmeters connected to measure the 3 phase power, if the current coils of the wattmeters are inserted in the lines R and Y. Tutorial Ans: WR = 2907.2 W WY = 7489.5 W

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