48 THE BELL SYSTEM TECHNICAL JOURNAL, JANUARY 1954 



bCR 



1 15 2 3 4 5 6 8 10 15 20 30 40 50 60 80 100 



U 



where « = 



(R = 



/«(« + V?/^ - l) COSH-h 



27r6 



2x& 



and 6 = length of each cylinder 



Fig. 14 — Reluctance between parallel cylinders. 



For other configurations \vhic'h bear a reasonable resemblance to the 

 above cases, the leakage reluctances can be estimated satisfactorily by 

 judicious modifications of the expressions for the simple cases. 



For example, consider the case of two parallel rectangular bars. They 

 are roughly eciuivalent to two parallel circular cylinders provided the 

 minimum separation is the same in both cases, and provided the perime- 

 ter of each cylinder is equal to the perimeter of the corresponding bar. 

 Thus, to estimate the leakage reluctance between the rectangular bars, 

 the radius of each equivalent cylinder is taken as \/2iv times the perime- 

 ter of the corresponding bar, and the center-to-center distance between 

 the eciuivalent cylinders is taken as the minimum separation between 

 the two bars plus the two equivalent radii. 



Leakage between the legs of many magnet forms may be estimated by 



