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CHAP. 11]

POLYPHASE CIRCUITS

257

Fig. 11-16

Three-Wire Without the neutral conductor, the Y-connected impedances will have voltages which vary considerably from the line-to-neutral magnitude. EXAMPLE 11.7 Figure 11-17(a) shows the same system as treated in Example 11.6 except that the neutral wire is no longer present. Obtain the line currents and find the displacement neutral voltage, VON .

Fig. 11-17 The circuit is redrawn in Fig. 11-17(b) so as to suggest a single node-voltage equation with VOB as the unknown. VOB  VAB VOB VOB þ VBC þ þ ¼0 ZA ZB ZC   1 1 1 150 2408 150 08 VOB þ þ ¼  6 08 6 308 5 458 6 08 5 458 from which VOB ¼ 66:76 152:858 V.

Then, IB ¼ 

VOB ¼ 11:13 2:858 A ZB

From VOA þ VAB ¼ VOB , VOA ¼ 100:7 81:088 V, and IA ¼ 

VOA ¼ 16:78 98:928 A ZA

Similarly, VOC ¼ VOB  VCB ¼ 95:58 18:588 V, and IC ¼ 19:12 116:48 A

Mahmood_Nahvi_eBook_Schaum_s_Outlines_Theory_An  
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