THE TRANSFORMER 



195 



because the losses are so small a part of the output that a large 

 percentage error in their measurement will make only a small 

 error in the efficiency. As the output and the input are so nearly 

 equal, it is difficult to determine the efficiency accurately by 

 direct measurement. 



Figure 182 shows the voltage characteristic and the efficiency 

 of a 100-kv-a., 60-cycle, 2,200/122 to 144-volt transformer 

 plotted airainst load. It will he noted that the efficiency is high 

 and is practically constant from J load to 25 per cent, overload. 



10 20 SO 



100 



120 





40 50 CO. TO 60 90 

 Kilowatt Output : P. F.=1.0 



. -Characteristics of a 100 kv-a., 60-rycle tninsfonncr. 



86. Core- and Shell-type Transformers. Transformers are 

 divided into two general types, the <<> retype and the shell type. 

 These two tyjx's din* i in the arrangement of the iron and 



OOppei with i-esjieet to each other. 



In the core type of tran>fonner tlie winding "r the eoj)j)ei' 

 -urr<>uiid> the iron core. I'i-jiiK- 170, 172, and 173 are diagram- 

 matic nirrely. hut they represent core-type t I'M n>fonnel>. 1'lUHIv 

 183 (a) shows tli- 'incut of the core-type ; 



former. ] i- in tin- f.rm of :i hollow scpiare made up of 



1 laminations about 11 mil.- thick. These lain in 



