0195136047.pdf

180 TIME-DEPENDENT CIRCUIT ANALYSIS

(b) Find the equivalent components of the net-

work representing the effect at the terminals

A–B.

(c) Find the Thévenin impedance (or thedriving-

point impedance) as seen from the terminals

A–B.

3.1.12Repeat Problem 3.1.11 if the 60-Hz voltage and

the current at the terminals are given to beV=

100 V (rms),I=10 A (rms), power factor=0.8

leading.

*3.1.13Use (a) mesh analysis and (b) nodal analysis to
determine the current through the 4-resistor of
the circuit of Figure P3.1.13.
3.1.14Use (a) mesh analysis and (b) nodal analysis to
determine the voltageV ̄at the terminalsA–Bof
Figure P3.1.14.
3.1.15(a) Obtain a Thévenin equivalent circuit at termi-
nalsA–Bin the circuit of Problem 3.1.14.
(b) What impedanceZ ̄L, when connected toA–B,
produces maximum power inZ ̄L?
(c) Find the value of the maximum power inZ ̄L.
3.1.16In the circuit of Problem 3.1.13, find the Thévenin
equivalent of the network as seen by the 4-

resistor, and then determine the current in the 4-

resistor.

3.1.17A 6.6-kV line feeds two loads connected in par-

allel. LoadAdraws 100 kW at 0.6 lagging power

factor, and loadBabsorbs 100 kVA at 0.8 lagging

power factor.

(a) For the combined load, calculate the real

power, reactive power, volt-amperes, and line

current drawn from the supply.

(b) If the power factor on the supply end is to be

unity, determine the value of the capacitance

to be placed across the load if the frequency

of excitation is 60 Hz.

*3.1.18Three loads in parallel are supplied by a single-

phase 400-V, 60-Hz supply:

LoadA: 10 kVA at 0.8 leading power factor

LoadB: 15 kW at 0.6 lagging power factor

LoadC: 5 kW at unity power factor

(a) Find the real power, reactive power, volt-

amperes, and line current drawn from the

supply by the combined load.

(b) If the supply line is to operate at 0.9 leading

power factor, determine the value of the ca-

pacitance to be placed across the load.

−

+

20 ∠ 0 ° V

2 ∠− 30 ° A

j 24 Ω

−j 4 Ω

4 Ω

10 Ω

18 Ω

8 Ω

Figure P3.1.13

−

+

−

+

−

+

−

+

12 ∠ 0 ° V V 1

A

B

−j 2 Ω V

−j 1 Ω

1 Ω

3 Ω

2 Ω

3 V 1

Figure P3.1.14