114 CONSTANT- VOLTAGE TRANSMISSION 



This gives, 



for n = 7 and p = ' i, L = (103.3 + 74I-I3 lgio ) 10"^ 



for n = 19 and p = 2, L = ( 89.3 + 741.13 log ) lo"" 6 



forw = 37and/> = 3, L = ( 85.1 + 741.13 log jio" 6 



for n = 6 1 and /> = 4, L = ( 83.3 + 741.13 log J lo" 6 

 and for solid wire, 

 n = i and p = o, L = ( 80.5 + 741.13 kfewTy I0 " 6 



A three- wire strand (Fig. 14 a) is a special case, since 

 there is no central wire. The inductance is 



5i / 2 V'T-h i\ 4 



L = 2 loge h T + 2 loge \ J loge 2 per cm. 



V 6 3 X 3 



Therefore, L = (125.2 + 741.13 log J lo" 6 henrys 



per mile, where p is the radius of the circumscribing 

 circle of the cable. 



The above equations may be put in the following 

 simplified form, which is more convenient for calculating. 

 No. of wires in strand. Inductance per mile, in henrys. 



3 ...... = 741-13 og--X 10"* 



7 ... . . . L = 741-13 log 2 ' d X lo" 6 



2. 6405 _6 

 19 ...... L = 741.13 log X 10 



37 ..... . L = 741.13 log ' X lo 



