文档介绍：Basic Circuit Theory
Chpter11Problems
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1 With reference to the circuit shown in Fig. 11-22, let V an =12 ∠0 kV and assume “+ ” phase
sequence. The balanced source supplies 1MW and VAR. If R w =12 Ω, find: (a) the line
current; (b) Z P ; (c) the transmission efficiency.
R w
R w
c C
i C 100µF
+
•• Z p
V c n V a n
−+ *
n -+a N
Z p A 100µF *
20i C
•−+ -
Z p
V b n
200cos500tV
+ -
R w
b B
Fig. 11-22 For . Fig. 11-23 For .
2 Find the reading of the wattmeter in Fig. 11-23
3 A balanced three-phase system has a ∆− connected load with 10+j4 Ω in each phase and is
supplied by a source with V L =250V. (a) Find the line current and the total power drawn by the
load. (b) To what minimum value can the line current be reduced by installine equal capacitive
reactances across each phase? (c) What size capacitors should be used at 60 Hz? (d) With the
capacitors in phase what is the total power delivered to the load?
4 A balanced 230V three-phase source is furnishing 6kVA at PF lagging to two
∆− connected parallel loads. One is a purely resistive load drawing 2kW. Determine the phase
impedance of the second load.
5 A 230V (line voltage) balanced three-phase system contains a ∆− connected load having
12+j3 Ω per phase and also a Y- connected load with 5+j1 Ω per phase. Find the