HW3_solutions - ECE 333 Homework 3 Solutions : Spring 2010...

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ECE 333 Homework 3 Solutions :: Spring 2010 1 A 345-kV three-phase line supplies 750 MVA at 0.8 pf lagging to a three-phase load which is delta connected. It is easiest to solve this problem in reverse order. .. d. Compute the total complex power. S 3 ! ! 750 ! cos " 1 ! 0.8 ! MVA ! 750 ! 36.87 o MVA ! 600 ! j450 MVA c. Compute real and reactive power per phase. S ! # S 3 ! 3 # 250 $ 36.87 o MVA # 200 % j150 MVA b. Find the magnitudes of the line and phase currents. Line current: S ! 3 ! V L !! I L ! ' 750 MVA # ! 3 ( 345 kV ( ! I L ! ' ! I L ! # 1255 A Phase current: ! I ! ! # ! I L ! ! 3 # 1255 ! 3 ' ! I ! ! # 724.57 A a. Find the complex impedance per phase. Z ! # V ! I ! # 345 $ 0 o kV 724.57 $" 36.87 o ' Z ! # 476 $ 36.87 o )# 380.8 % j285.6 ) 2 A three-phase wye-connected motor draws 40 kVA at 0.65 PF lagging from a 230 V (line-line) source. A wye- connected capacitor bank is connected across the motor terminals to improve the PF to 0.95 lagging. a. Find the kVAR rating of the capacitor bank.
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HW3_solutions - ECE 333 Homework 3 Solutions : Spring 2010...

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