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678 ⏐⏐⏐ SERIES AND PARALLEL ac CIRCUITS<br />

–<br />

B L – B C<br />

j<br />

B C ∠ 90°<br />

G ∠ 0°<br />

B L ∠ –90°<br />

–50.194°<br />

0.195 S<br />

Y T<br />

FIG. 15.94<br />

Admittance diagram for the parallel R-L-C<br />

network of Fig. 15.92.<br />

+<br />

XL � qL � (1000 rad/s)(4 mH) � 4 �<br />

1<br />

1<br />

XC ����� �10 �<br />

qC (1000 rad/s)(100 mF)<br />

The network is redrawn in Fig. 15.93 with phasor notation. The total<br />

admittance is<br />

YT � YR � YL � YC � G �0° � BL ��90° � BC ��90°<br />

1 1<br />

1<br />

� � �0° � � ��90° �� ��90°<br />

8 � 4 � 10 �<br />

� 0.125 S �0° � 0.25 S ��90° � 0.1 S ��90°<br />

� 0.125 S � j 0.25 S � j 0.1 S<br />

� 0.125 S � j 0.15 S � 0.195 S ��50.194°<br />

I = 12 A ∠ 0°<br />

Y T<br />

+<br />

E<br />

–<br />

R 8 � 4 �<br />

X L<br />

FIG. 15.93<br />

Applying phasor notation to the network of Fig. 15.92.<br />

b. See Fig. 15.94.<br />

c. E � IZT � � � 61.538 V �50.194°<br />

IL � � � � 15.385 A ��39.81°<br />

d. Fp � cos v � � � 0.641 lagging (E leads I)<br />

P � EI cos v � (61.538 V)(12 A) cos 50.194°<br />

� 472.75 W<br />

e. ZT � � � 5.128 � ��50.194°<br />

� 3.283 ��j 3.939 �<br />

� R � j XL XL � 3.939 ��qL<br />

L � � � 3.939 mH<br />

The series equivalent circuit appears in Fig. 15.95.<br />

f. E � IZT � (12 A �0°)(5.128 � �50.194°)<br />

� 61.536 V �50.194° (as above)<br />

g. P � I 2 R � (12 A) 2 (3.283 �) � 472.75 W (as above)<br />

(3.283 �)<br />

h. Rp � � � 8 �<br />

2 � (3.939 �) 2<br />

R<br />

���<br />

3.283 �<br />

2 s � X 2 I 12 A �0°<br />

� ���<br />

YT 0.195 S ��50.194°<br />

VL E 61.538 V �50.194°<br />

� � ���<br />

ZL ZL 4 � �90°<br />

G 0.125 S<br />

� �<br />

YT 0.195 S<br />

1<br />

1<br />

� ���<br />

YT 0.195 S ��50.194°<br />

3.939 � 3.939 �<br />

� ��<br />

q 1000 rad/s<br />

s<br />

�<br />

Rs<br />

I L<br />

X C<br />

10 �<br />

a c

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