38 Proceedings of the Royal Society of Victoria. 



We have (see ^33) 



]f2vn.2G^=l'2.b . 10'° + Secondary copper loss, and the secondary 

 copper loss may in this connection be neglected in a rough deter- 

 mination of T ; but 



«A=^2 . ^ . Ub'=\b.QUly\ 



F=y . p . 4/3/3'=17450^/?', 



taking the values ^2=12.91, y=4847 already used; hence 



12 5 1 0^° 



bb'BB'= • =3030, 



^^ 507r . 15.05 . 17450 



which with the ratios ^jb above enables us to determine (i and b 



in each case. 



The formula for the numeric t can be put in the form 

 _ TT/x Output _ 3,925.000 



''~2pcy {/3+(3' + 2b){b±b' + /3)~{^+p' + 2b) {b + b''+ P) 

 by means of which its values in the five special cases considered 

 can be determined. 



Thus we obtain the following details given in tabular form. 



We also find that the iron losses at full load, which are half the 

 total losses, are for (a) 192.5, (/;) 189.9, (c) 186.8, (d) 184.2, 

 and (e) 181.4 watts, so that transformer (e) is the most efficient 

 of the series, having an efficiency at full load of 97.2 per cent. 

 Obviously the transformer designed in detail with square 

 windows and square tongue is of a less efficient shape than any 

 of these, as its iron loss at full load is 200.3 watts. 



The volume of iron in each of the present series in cub. cms. 

 is 100 times the iron loss in watts. In {e) it is 18140 cub. cms., 



