Abstracts of Technical Articles from Bell System Sources 



The Orientation of Crystals in Silicon Iron} Richard M. Bozorth. 

 X-ray examination of silicon iron prepared by N. P. Goss shows that 

 the component crystals are oriented so that a C^Ol] direction is 

 parallel to the direction of rolling and a (110) plane lies in the rolling 

 plane. This is contrary to the result reported by Goss in his paper 

 "New Development in Electrical Strip Steels Characterized by Fine 

 Grain Structure Approaching the Properties of a Single Crystal," 

 published in Transactions of the American Society for Metals, Volume 

 13>, June, 1935, page 511. The differences in the magnetic properties in 

 different directions in the sheet are explained in terms of the properties 

 of the single crystals. 



Eddy Currents in Composite Laminations} E. Peterson and L. R. 

 Wrathall. The familiar theory of eddy current shielding leads to 

 an expression for the impedance of a ferromagnetic core inductance 

 coil in terms of the initial permeability and resistivity of the core 

 material, the core geometry, and the measuring frequency. Measure- 

 ments on a numb&r of different core materials over a wide frequency 

 range have revealed sizeable deviations from the theory in some cases. 

 The discrepancies are especially marked in some specimens of 

 chromium permalloy, the measured inductance over a certain fre- 

 quency range being of the order of one tenth that specified by the 

 theory. 



It appears that discrepancies arise when the laminations are not 

 homogeneous, a condition contrary to an assumption of the simple 

 theory. The inhomogeneity takes the form of a thin surface layer 

 which has a permeability much less than that of the interior. By 

 etching off these surface layers, the initial permeability is increased, 

 and discrepancies between the measured variations of impedance with 

 frequency and those calculated for a homogeneous sheet are removed 

 almost completely. 



The theory has been extended to take account of the surface layers, 

 and agrees well with measurements on the original unetched lamina- 

 tions when plausible assumptions are made regarding the properties 

 of the surface layer. 



' Transactions, Amer. Soc. for Metals, December, 1935. 

 ^Proc. I. R. E., February, 1936. 



349 



