124 Mr. R. L. Wills on the Hysteresis Loss in Tr 



of transformers is cine to prolonged heating at comparatively 

 low temperatures. The experiments of Parshall * aDd Roget f 

 show that this increase of hysteresis in iron does not always 

 take place, and that in specimens of inferior magnetic quality 

 the rise in hysteresis is much less than in the best specimens 

 of transformer iron. 



Fig\ 2. 



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^E=24-Uxrs 

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In order to render the values of the hysteresis at different 

 temperatnres comparable, the specimen, which when annealed 

 was of inferior magnetic quality, was first heated to about 

 800° C. and allowed to cool rapidly. In this condition the 

 values of the hysteresis did not sensibly increase by prolonged 

 exposure to any temperature. 



The specimen having been demagnetized by reversals 

 values of U x for various inductions were first obtained, using 

 a battery of 8 volts, and afterwards a corresponding series of 

 readings for U 2 was taken for the same magnetic forces 

 using a battery of 16 volts. From these two sets of readings 

 the hysteresis losses for different values of the maximum in- 

 duction were found from the formula W=2TJ 1 — U 2 as 

 described above. The results for different temperatures are 

 recorded in Table II.. and are shown graphically in fig. 3 

 (p. 126). 



Morris i has investigated the effect of temperature on the 

 hysteresis loss of specimens of soft iron for a range of in- 

 duction of +4550 : his curves giving the values of the 



* Minutes Proc. Inst. C. E. toI. cxxvi. p. 244 (1896). 

 t Proc. Eov. See. vol. kiii. pp. 258-267 (1898). 

 I Phil; Mag. vol. xliv. pp. 213-254 (1897). 



