66 Proceedings of the Royal Society of Victoria. 



Let 26, 26' be the dimensions of the rectangular windows, or 

 winding apertures in the laminae, the coils being wound round 

 the lb' dimension, 2/3 the width of the iron strip, and 2/3' the 

 dimension of the core measured perpendicular to the laminae, 

 then 



a = ibb', /=4:{P + (3' + b), 



a = 4/3^', \ = 4:{d + b' + 2(3). 

 and we find as in § 56, or by simply interchanging /3 and b, 

 /3' and b' in I., § 56, that for maximum r, that is maximum 

 efficiency 



6(3^-yS') = 2/3(/3'-2/3), 



b{b'-2b)=p{3b-b'). 



If b' = ib, fi' = rj^, and /S^z/i as before, 



• 3u + 2 iu + 3 



^=17TT' ^ = 2^7:^' ^"-^ 



and the equation of the losses is 

 (3?/ + 2)(6?/''' + 6?/ + l) /I 



provided the coils are wound in a number of alternate layers so 

 that the mean lengths of the primary and secondary turns are 

 equal. 



From this equation u can be found, and thence by II., $ and rj. 



The equation of the output (see § 56, IV.) 



gives h, which with ?/, ^ and rj, determine the transformer. 

 In this case 

 ^ tt/aP^ 1 



2pC^yV' ( 1+ ^ + 2?^) ( 1 + ?/ + llrj) 

 For example, if 



P,= 12.5 K.W. as before, 

 then ?^ = . 876, ^=2.47, -7=2.36, 6 = 5.1, 



and T=7320, just the least thing better than the maximum 

 efficiency transformer of the shell type. 



