MAGNETIC MATERIALS IN TELEPHONE SYSTEM 



447 



Other materials are also listed in Table I. Manufacturing tolerance 

 limits are frequently somewhat less favorable than here indicated. 

 In the section on laminated cores in Table IV, the eddy current coeffi- 

 cient e has been computed for several common sheet thicknesses. 

 Values for other thicknesses can be calculated as proportional to the 

 square of the thickness ratios. 



TABLE IV 

 Alternating Current Loss Data on Sheet and Powdered Materials 



Material 



Size 



Perme- 

 ability 



Resis- 

 tivity 



pXlOs 



Hys- 

 teresis 

 Coeff. 

 aXlOs 



Re- 

 sidual 

 Coeff. 

 cXlQs 



Eddy 



Current 



Coeff. 



eXlO' 



Laminated Cores 



45 Permalloy . . 

 45 Permalloy . . 

 78.5 Permalloy . 



4-79 Mo-Permalloy . . . 

 3.8-78.5 Cr-Permalloy 

 45-25 Perminvar 



7.5^5-25 Mo-Perminvar. 



2 V-Permendur 



4% Silicon Iron 



Magnetic Iron 



14 mil sheet 

 3 mil sheet 

 6 mil sheet 



6 mil sheet 

 6 mil sheet 

 6 mil sheet 



6 mil sheet 

 14 mil sheet 

 14 mil sheet 

 14 mil sheet 



1,160 



53 



600 



173 

 146 

 505 



120 

 2,000 



870 

 5,200 



Loading Coil Cores 



Isoperm '^ 



Grade B Iron Powder. 

 Grade C Iron Powder. 



81 Permalloy Powder 



2-81 Mo-Permalloy Powder 



Sendust ^^ 



Ferrocart '* 



1.7 mil sheet 



80 mesh powder 



200 mesh powder 



120 mesh powder 

 120 mesh powder 

 120 mesh powder 

 5 micron powder 



15 

 88 

 31 



51 



17 

 4.0 

 0.8 



Mechanical Sensitivity 

 Stresses beyond the elastic limit in soft magnetic materials should 

 be avoided if possible, since they lower the permeability, and in general 

 increase the hysteresis loss. A partial exception to this statement is 

 found with the " Isoperms " (essentially 50 per cent Ni, 50 per cent Fe). 

 These alloys, after excessively hard rolling, annealing, and final moder- 

 ately hard rolling, develop low permeabilities and low hysteresis losses 



i«0. Dahl & J. Pfaffenberger, Zeit.f. tech. Phys. 15, 99 (1934). 



" H. Masumoto, Tohoku Sci. Rep. Honda Anniv. Vol., p. 388 (1936). 



i« M. Kersten, Elektrotech. Zeit. 50, 1335 (1937). 



