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834 ⏐⏐⏐ NETWORK THEOREMS (ac)
Next, the short-circuit current will be determined using IPRINT as
shown in Fig. 18.103, to permit a determination of the Thévenin impedance.
The resistance Rcoil of 1 m� had to be introduced because inductors
cannot be treated as ideal elements when using PSpice; they must
all show some series internal resistance. Note that the short-circuit
current will pass directly through the printer symbol for IPRINT. Incidentally,
there is no need to exit the SCHEMATIC1 developed above
to determine the Thévenin voltage. Simply delete VPRINT and R3,
and insert IPRINT. Then run a new simulation to obtain the results of
Fig. 18.104. The magnitude of the short-circuit current is 0.936 A at an
angle of �108°. The Thévenin impedance is then defined by
ETh 5.187 V ��77.13°
ZTh ��� �� �5.54 � �30.87°
Isc 0.936 A ��108.0°
which is an excellent match with 5.49 �
�32.36° obtained in Example 18.8.
FIG. 18.103
Using PSpice to determine the short-circuit current.
VCVS The last application of this section will be to verify the results
of Example 18.12 and to gain some practice using controlled (dependent)
sources. The network of Fig. 18.50, with its voltage-controlled
voltage source (VCVS), will have the schematic appearance of Fig.
18.105. The VCVS appears as E in the ANALOG library, with the voltage
E1 as the controlling voltage and E as the controlled voltage. In the
Property Editor dialog box, the GAIN must be changed to 20 while
Th