ARMATURE LAMINATIONS 



23 



The instrument is illustrated in Fig. 11, and is known as the 

 Blondel-Carpentier Hysteresimetre. In this instrument the 

 density is about 10,000 lines per sq. cm. The results on any 

 sample are reduced, by comparison of the deflection with the 

 deflection obtained on 'a standard sample, to terms of the loss in 

 ergs per cu.cm. per cycle for a density of 1 line per sq. cm. 



This value, i.e. the hysteresis loss in ergs per cycle in 1 cu.cui. 

 of iron, and corresponding to a 

 density of 1 C.G.S. line per sq. cm., 

 is called the Steinmetz Coefficient, 

 and is generally denoted by >/. As 

 the specific gravity of sheet iron 

 may be taken as about 7*8, it is 

 evident that 1 kg. of sheet iron 

 contains 



1000 

 7'8 



= 128 cu.cm. 



Hence, if the hysteresis loss 

 per cycle per cu.cm. for a density 

 of 1 line per sq. cm. is equal to 

 ?; ergs, then the hysteresis loss 

 per cycle per kg. for a density 

 of 1 line per sq. cm. is equal to 



128 rj ergs, 



and the hysteresis loss per kg. 



for a density of 1 line per sq. cm., and for a periodicity of 



50 cycles per second, will be equal to 



50 x 128 x rj ergs per second, 



= 6400 rj ergs per second, 



6400 



FIG. 11. Hysteresimetre. Blondel- 

 Carpentier. 



= 0-00064 



watts, 



watts. 



It would, for practical purposes, have been more convenient if 

 the Steinmetz Coefficient had been originally defined as the loss 

 in watts per kg. for a given periodicity, and for a density of 

 1 line per sq. cm. As, however, the practical man, when buying 

 iron, is frequently obliged to compare data in which the hysteretic 

 quality is guaranteed in terms of rj (the Steinmetz Coefficient), 

 there are given in Table VII., in parallel columns, the equivalent 

 values for irons of various hysteretic qualities. 



