84 



BEl.I. SYSTFM Tf.CHKlCAL JOCKX.IL 



niiiliial impedance. Similari\-, wlit-n a mutual impedance acts in such 

 a way as to decrease vcctorially the impedance of such a combination, 



Fig. 22 — Miitii.il linpidaiue Acting Between Two Si'lf Impedances Connectei 

 in Scries 



it is lallcd a series opf>osiii'^ iiiiiliiul iniprilniue. For i-xampk-, if the 

 total impedance. Z, of the combination shown in Fij;. 22 is 



y y {IZi + IZm) + (IZ, + IZ.X,) y ,y ,.^y „„. 



/C — J = J =Zi+z-..+.^z.\/ (,/■■») 



the mutual impedance is scries aiding. On (he oilur hand, if the total 

 inipedaiicc. /. nl the combination is 



7_l' (IZ, +IZm)+(IZ,+ IZm ) y ,y _ ,_,, 



the mutual impedance is series opposing. 



'J'ransfonner Represenlation. If, in Fig. 22. Zi represents the self 

 impedance of one winding of a transformer and Z- tiie self iin|)edaiice 



I o nmr^ 



-hfTin- 



-o 3 



l-'ig. 2.?— 7' .Network Coiilaining Two Self Inipediinces.'H.iviiiK Miilu.il Inip.d.mr 

 Hel ween Tliein 



of its other winding, the series impedance of the two windings (between 

 terminals 1 and W in Fig. 23), as given i)y equations {l'.^) and (74), will 

 rletermine whether the mtilual imped, nice, Z.i/, is series .lidiiig or 

 M-ries opposing. 



The mutual impedaiKe between the two windings ma\ be repre- 

 sented by an equivalent network of self imjiedances connected 



