C HAP. Ill] HYSTERESIS AND EDDY CURRENTS 47 



obtained directly from actual machines will be found in his several 

 books on electric machine design. 



It is customary now to characterize a lot of steel laminations 

 with respect to its core loss by the co-called figure of loss (Verlust- 

 ziffer) , which is the total core loss in watts per unit of weight, at a 

 standard frequency and flux density. In Europe the figure of loss 

 is understood to be the watts loss per kilogram of laminations, at 

 < les and at a flux density of 10 kilolines per square centimeter; 

 the test to be performed in an Epstein apparatus under definitely 

 prescribed conditions. 1 Sometimes a second figure of loss is 

 required, referring to a density of 15 kilolines per square centi- 

 meter, when the laminations are to be used at high flux densities. 

 In this country a figure of loss is sometimes used which gives the 

 watts loss per pound of material at 60 cycles and at a flux density 

 of 60 kilolines per square inch (or else at 10 kilolines per square 

 centimeter; see the paper mentioned in problem 20 below). 



In some cases it is required to estimate the hysteresis and the 

 eddy current losses separately ; also it is sometimes necessary to 

 separate the two losses knowing a curve of the total loss. These 

 calculations are explained in the articles that follow. 



Prob. 13. The core of a 60-eycle transformer weighs SO kg.; the, 



gross cross-section of the core is 8 by 10 cm., of which 10 per cent is taken 



by the insulation between the laminations. The total flux alternates 



ii the values of 0.49 megaline. If the core i-^ made of gauge 26 



good carbon steel, what is the total core loss according to the curves in 



iO? Solution: The flux density is l'.M)/(8X 10x0.9) -6.8 Id/so,. cm. 



The core loss per ruble decimeter at this density :md at t>0 cycle- is 



ling to the curve, equal 11.5 watt. The volume of the laminations. 



including the in-ulation, is 89/7-12.7 eu. dm. The total loss is 11..". 



12.7 Mi. watt A. is. i i> 



Prob. 14. What flux density could Ix; used in the preceding problem 

 if the made of >ilicoii->tcc| laminations, gauge 29. provided that 



the total core loss be kept the same in both cases? 



\ ft About '. kl s.j. cm. 



Prob. 16. Calculate the core loss ill the -L.tionary armature of ji 60- 

 cydc |.")()-r.p.m. alternator of the following dimensions: l>ore ISO . m.; 

 gross axial length L'l cm.: two air-du --adial width of 



l.'i .in.; the machine has 144 *! 



\\ide Kiuigr Kx>d carbon steel; 



the useful flux per pole is 4.65 meg.-' ! t\\o third-. <>i tin- total num- 



i carry the flux simultaneously . CM- Mi I! 



See EUktrrttchriick* ZeiUrhrifi. v,.| -i (1003), p. 684. 



