igii.] 



WHITEHEAD— HIGH VOLTAGE CORONA IX AIR. 



381 



TABLE III. 



circular conductor having the same critical voltage as that observed 

 for the cable (column c) and the diameters of the circle just enclos- 

 ing the cable (a) and that given its equivalent section (b). The 

 ratios b/c and c/a are given in the last two columns, and are plotted 

 in their relation to the number of strands in Figs. 3 and 4 respec- 

 tively. Fig. 3 indicates that if instead of a solid conductor a 

 stranded conductor of equivalent cross section be used the critical 



3 6 7 



NwMBer? Of Str^hoS. 



Fig. 3. 



voltage will be lowered, but by less than three per cent, if the num- 

 ber of strands is greater than 5. For a three-strand cable the lower- 

 ing is ten per cent. 



The ratio c/a is more important however. This ratio compares 

 the diameter of a solid conductor having the same critical voltage 

 as the cable, with the actual overall diameter of the cable. It there- 

 fore refers the behavior of a given cable, with regards critical 

 voltage, to a solid round wire whose diameter is expressed as a 

 fraction of the overall diameter of the cable. This is a more logical 



