Sfo/lo.)/. 327 



Avhere a, /3 and r are constants for the material, n the fre- 

 quency and ^ is the " eflfective induction," a quantity of great 

 importance in the calcuhition of the eddy current loss (E), as 

 will be explained later. 



The method employed was similar to that described by 

 Professor Lyle'. By means of his wave-tracer'- the wave forms 

 of the mairnetiziny cvirrent and the resultant magnetic tlux 

 pulsating in the iron can be accurately determined. Tlie full 

 wave being obtained, fifteen ordinates per half wave were taken, 

 from which, without plotting, the first, third and fifth har- 

 monics composing the waves can be calculated. Two methods 

 of harmonic analysis were used (1) for approximately sinusoidal 

 waves, that devised by Lyle', (2) for waves into which har- 

 monics higher than the fifth entered consideral)ly, that of 8. P. 

 Thompson*. 



The wave forms having been analysed, the results were re- 

 duced to absolute measure by the apiDlication of pro^^er factors^. 

 The magnetizing force and induction w^ere thereby obtained in 

 the form — 



H = Hj[sinoj/+ A^sin3(w/ - </>.,) + /'.5sin5(W -</>-)+ ] 



B = B,[sin(oj/ -6) + A^sin3(a)/ - $,) + A-,sin5(W -0,)+ ] 



In general, harmonics higher than the fifth were neglected 

 and are not given in the tables. In calculating the total losses, 

 however, these upper harmonics were included. 



From these equations the value of the total loss per c.c. per 

 cycle— 



1 = 1 fudn 



47ry 



4 



is determined. 



The amount of eddy-ciirrent loss per c.c. per cycle (E) was 

 calculated from the approximate formula given by Searle and 

 Bedfordl 



1 T. K. Lylf. l-liil. .Mat,^, 1!)0.=>, vol. ix. 



2 T. K. L.vle. I'liil. Ma^., 19(W, vol. vi. 



3 T. R. Ljle. Phil. Ma<,'., 190U, vol. xl., also Proc. Roy. Hoc. \ ictoiia, vol. x\ii. 



4 S. v. Thompson. Klectiioiaii, lOOf.. 



5 Searle and Hedfonl. I'hil. Trans., 190-2, App. 



