FERRITE CORE INDUCTORS 



277 



From (24) 



and 



A = ("00159 +^001)0-02 ^ 0.00024 



D = i)o + I>c = 0.00183 



or the actual measured Q of the large inductor is 550, about half that 

 indicated by core loss considerations alone. 



EFFECT OF CORE PROPORTIONS ON DISSIPATION FACTOR 



In the foregoing discussion of coil volume it has been assumed that the 

 core porportions remained fixed as the volume was changed. It is now 

 of interest to know what these proportions should be to insure the lowest 

 dissipation. 



The general type of structure under consideration consists of a closed 

 cylindrical container and a center post of magnetic material, and an air 

 gap which might be anywhere in the magnetic path. It is assumed that 

 the thickness of the shells is such that the area of the magnetic path is 

 uniform and equal to the area of cross section of the post. It is also as- 

 sumed that the flux is uniformly distributed within the cross-section of 

 the core. Fig. 5 represents such a core schematically. 



Given a fixed over-all coil volume it is desired to know what proportions 

 should apply to the outside diameter, the diameter of the center post 

 and the axial height of the structure, to provide the lowest dissipation 

 factor. This will be examined first for the case where residual or eddy 



HR 



I I 



[*- PR--H I 



^ R -^ 



Fig. 5 — Optimum proportions for post and shell core assembly. 



