Two balanced three-phase loads that are connected in parallel are fed by a three-phase line having a series impedance of ( 0.4 − j 2.7 ) Ω per phase. One of the loads absorbs 560 kVA at 0.707 power factor lagging, and the other 132 kW at unity power factor. The line-to-line voltage at the load end of the line is 220 3 V . Compute (a) the line-to-line voltage at the source end of the line. (b) the total real and reactive power losses in the three-phase line, and (c) the total three-phase real and reactive power supplied at the sending end of the line. Check that the total three-phase complex power delivered by the source equals the total three-phase comp lex power absorbed by the line and loads.
Two balanced three-phase loads that are connected in parallel are fed by a three-phase line having a series impedance of ( 0.4 − j 2.7 ) Ω per phase. One of the loads absorbs 560 kVA at 0.707 power factor lagging, and the other 132 kW at unity power factor. The line-to-line voltage at the load end of the line is 220 3 V . Compute (a) the line-to-line voltage at the source end of the line. (b) the total real and reactive power losses in the three-phase line, and (c) the total three-phase real and reactive power supplied at the sending end of the line. Check that the total three-phase complex power delivered by the source equals the total three-phase comp lex power absorbed by the line and loads.
Solution Summary: The author explains the line-line voltage at the source end and the expression for the per phase current.
Two balanced three-phase loads that are connected in parallel are fed by a three-phase line having a series impedance of
(
0.4
−
j
2.7
)
Ω
per phase. One of the loads absorbs 560 kVA at 0.707 power factor lagging, and the other 132 kW at unity power factor. The line-to-line voltage at the load end of the line is
220
3
V
. Compute (a) the line-to-line voltage at the source end of the line. (b) the total real and reactive power losses in the three-phase line, and (c) the total three-phase real and reactive power supplied at the sending end of the line. Check that the total three-phase complex power delivered by the source equals the total three-phase comp lex power absorbed by the line and loads.
Determine the required EMT size for the following combination of conductors:18. Four 8 AWG Type THW and four 12 AWG Type THW:19. Three 350 kcmil and one 250 kcmil Type XHHW conductors and a 4 AWG bare conductor:20. In a nonmetallic-sheathed (Type NM) cable installation, a 10⁄3 with equipmentgrounding conductor is installed in a metal octagonal box to supply two 12⁄2 withequipment grounding conductor branch-circuit cables. What is the minimum sizebox? The box contains internal cable clamps
For problems 8 and 9, determine the correct box size for each of the following conditions:8. Two nonmetallic sheathed cables with two 12 AWG conductors, an equipment groundingconductor, and a switch in a metal box without a plaster ring.9. A raceway run serving a series of luminaires, connected to a total of three circuits. Theluminaires are supplied by 120 volts from a 3-phase, 4-wire system. Each box will containtwo circuits running through the box and a third circuit connected to a luminaire, which issupported by a luminaire stud in the box. Use 12 AWG Type THHN conductors.
28. The minimum size raceway for the following conductors is: a. Three, 250 kcmil conductors with XHHW insulation b. One, 3⁄0 AWG conductor with XHHW insulation c. One, 4 AWG conductor with XHHW insulation29. The minimum size raceway for the following conductors is: a. Twelve, 6 AWG conductors with THHN insulation b. Nine, 8 AWG conductors with THHN insulation c. Eighteen, 10 AWG conductor with THHN insulation d. One, 10 AWG equipment grounding conductor with THHN insulation30. The minimum size wireway for the following with parallel conductors is: a. Two sets of three, 250 kcmil conductors with XHHW insulation b. Two, 3⁄0 AWG conductors with XHHW insulation c. 1, 4 AWG conductor with XHHW insulation d. The conductors terminate on three power distribution blocks. Each one has adimension of 4 in. wide and 3 in. high:
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