THE TRANSFORMER 185 



resistance of the transformer referred to the primary and is denoted 

 by #01- 



#01 = Ri + (~) "# 2 (50) 



The total copper loss may then be found by using the primary 

 current alone. That is 



P e = /i 2 #oi 



The equivalent resistance of the transformer referred to the 

 secondary may be found in a similar manner and is equal to: 



#02 =#2+ 



The total copper loss may be found by using the secondary 



current alone. That is 



PC = /2 2 #02 



These values of equivalent resistance may also be used in 

 determining the regulation of the transformer, as will be shown 

 later. 



In well-designed apparatus and for the most economical use 

 of the materials, the various parts should all come to their 

 limiting temperatures at the same time. As primary and second- 

 ary windings ordinarily occupy approximately the same volume, 

 their lonefl >hould be the same for equal temperature rise. That 



/!*#! = / 2 2#, 



Since 



ft Ai 



/i N, 

 #, = /,- _ A/V 



R, /r AT,' 



That is. under these assumptions the ratio of primary and 

 secondary resistance is equal to the square of the ratio of the 

 primary and secondary turns. 



Th-- primary leakage reactance drop is / : .V , and t he second- 

 ary leakage reactance drop is I^X*. I\X\ is a voltage and must 

 be to the same scale as the primary induced emf. / . l- 2 Xi is 

 likewise a voltage and is to the is the -econdary 



induced emf. A', It is convenient to use the same lenuth of 

 vector to represent l-l\ and /,'.. and lain correct these values 



