ECE 3364 HW 7, Spring 09, due 3/30
Problem 1.
Nilsson, seventh edition
Problem 10.61
Problem 2.
Nilsson, seventh edition
Problem 10.64
Problem 3.
A balanced 3-phase system has a Y-connected source (voltage and impedance rmsna VV °∠= 01365
~
',
2jZs=, positive phase sequence) connected to a transmission line (impedance Ω= 5.1
line
Z) which is
connected to an ideal step-down three-phase
Δ
−
Y connected transformer ( 4000
1
=
N,2000
2=N ) whose
secondary is connected to a Y-connected load (
Ω
+
=
−1145.85 jZ YL ). Find the phase current in the secondary
coil and total power delivered to the 3-phase load.
Problem 4.
A balanced 3-phase system has a three-phase Y-connected source (voltage and impedance
rmsna VV °∠= 01365
~
', 2jZs=, positive phase sequence) connected to a three-phase transmission line
(impedance Ω= 5.1
line
Z) which is then connected to an ideal three-phase Y-Y step-down transformer
(4000
1=N). The voltage across the Y-connected load on the secondary side of the transformer
(Ω+=
−1145.85 jZ YL ) is rms
V220 . Find the number of turns 2
N in the secondary windings.
Problem 5.
Consider a balanced 3-phase system with a Y-connected source having internal impedance
Ω
=
4
s
Z
connected to a 3-phase transmission line having impedance
Ω
+
=
86 jZline . The three-phase
transmission line is connected to an ideal 3-phase transformer whose primary and secondary number of
turns are 4000
1=N and 2000
2=N. The secondary side of the 3-phase transformer is connected to a Y-
connected load Ω+=
−410 jZ loadY . Determine which arrangement of the transformer leads would result in
the most power delivered to the load ?
(a) Δ−Y (b) Y−Δ (c) Δ−Δ or YY −