ENTBQDUCTOKX 



i imentiuLf was done before a commercial stage 

 Tin- matter was chiefly worked out by Mr. \\ . S. M 

 whom (ami also to Prof. Klihu Thomson) the development of 

 .nly the oil transformer, but also the air-blast transformer 

 (which was developed .simultaneously) was in <_^vat im a-uiv 

 due. At this time (1898 to 1895) there was a rapid increase 

 in the pressures employed in transformers. Up to ls'.'-J 

 i UH-S of 2000 to 3000 volts had only been exceeded in 

 3, but (hiring the immediately following years, 

 in. s of 10000 and even 20000 volts were fairly fre- 

 quently employed, and the general experience then was that 

 these piv>sinvs could be best handled with the air-blast type 

 As the reader knows, transmission plants are now 

 iP.MU) in operation where the transformers are wound for 

 80000 and even 100000 volts, but in Is'.U a 

 urc of 20000 volts was considered distinctly high. In 

 the manufacturers did not then build three-phase 

 tran I, but employed groups of three single-phase 



Another variant introduced by this time (1S1M to IS!).", ) was 



the increasing use of the low periodicity of -J."i cycles per 



id. This was ehietly brought about by the la 



. > ..htaiiieil with ."U-cycle and 60-cyelc rotai \ ters. 



illations where rotary converters were likely to be 



required it became u^ual to employ -J."i Ojolefl p r second, and 



thi- ; !y ha- ultimately found very considerable favour, 



units of advantages in transmission-line d< 

 also in 'ther dip cially a- .ts of 



and UK-tors. 



ii v..is nt until Isur, that I Was first given a really 

 ruble amount of responsible inning. Hut 



id atl'orded a good preliminan tl 



and I to,.k on the task \\ith much interest. I'.ut it is 

 only \\-li.-n one eomei right down to doing the actual task 

 that one is capable of fully I :ing the magnitude ol 



