176 Prof. J. Perry on the 



Of course, if B/ = co , there is further simplification: 



r=U, i=^W+WU, A=^ w = m ,= k " L nearly; 



tan e = 



JcL 

 R' 



e = 90° very nearly, 



A'- Ma -0 



tan e'= — r 



LA;' 



or e' is nearly 180°. 



Hence, if the periodic function is not merely a simple sine 

 function ; if R' is very great, the primary current is a very 

 different function of the time from the primary voltage, 

 whereas the secondary current and secondary voltage are the 

 same kinds of function of the time as the primary voltage. 



2nd. When W very small : 



l' = kL', 1=0, r = R + 

 and 



a- a 

 R + ^R' 



M 2 R' 



L' 2 ' 



2 = R + ^R', 



A' 



«M 



L'R + LR' 



tan e = 0, 



tan e'=0, 



>« 



(5) 



J 



Hence, in general, whatever be the law of current, both 

 the primary and secondary currents, and therefore the secon- 

 dary voltage, are the same functions of the time as the primary 

 voltage, and to calculate their dynamometer readings is very 

 simple. 



3rd. As a help to the memory, it may be remarked that 

 the primary current is just what it would be if there were no 

 secondary circuit and if the resistance and self-induction were 

 r and I respectively. 



When R/ is great, we have practically r = R and Z = L. 



When R' is small, 



r=U + -jj T and 1= j-, — ; .... (6) 



and as these do not involve the periodicity, we may say gene- 

 rally, whatever be the law of change of primary voltage in an 

 ordinary transformer, 



Y=rC+lC, 



