Ratio 



INSTRUMENT TRANSFORMERS r>87 



io = = /Jftj 



F- 2 \ # 2 2 



approximately. 



.r r 



Vz leads Vi, and tan 



As the phase angle may be either positive or negative, it is 

 necessary to be able to give Z 2 either a positive or negative reac- 

 tance. This may be accomplished if it is made up as shown in 

 Fig. 364. The condenser C 2 is shunted by a variable non-induct- 

 ive resistance r 2 ; L 2 is an inductance, 



F[<;. 8(>4. Arrangement for obtaining positive and negative reactances in 

 potential transformer tests. 



If o> 2 (7 2 2 r 2 2 is negligible compared to unity, 



That is, the circuit acts as if it had a resistance # 2 and an induc- 

 tance (L 2 C 2 r 2 2 ). The resistance r 2 may be varied by the 

 slider. The inductance Z/ 2 may have a fixed value; if so, it can 

 be placed at a distance from the vibration galvanometer and 

 other apparatus, thus avoiding trouble from stray fields. 



The vector solution for the ratio and phase angle, when the 

 connections shown in Fig. 363 are used, is obtained as follows. 



Referring to Fig. 365, the direction and magnitude of the line 

 ab which represents the drop across Z z may be controlled by 

 adjusting ft., an ,i L 2j anc j the point b may be made to coincide 



