Till-: TRANSFORMER 



223 



ondary 60 turns, the ratio will be 30:1. The ratio may vary 

 slightly from this value due to the magnetizing current. In Fig. 

 215 (a), the primary current /i consists of two components, 7 2 , 



mponent necessary to balance the secondary ampere-turns, 



and /,,, t he magnetizing current. The magnetizing current intro- 



a slight error in the ratio as well as causing 7 2 to depart by 



MU-le ft from the 180 phase relation to /i. At light loads 

 the magnetizing current may cause considerable error. Figure 

 215 (6) shows the variation of phase angle and ratio with load 

 for a typical transformer. 



(a) Vector diagram. 



100.5 



11000 



99.5 



fbaie Angle 



K1H 



Ratio 



2 >* 



456 

 Secondary Current 



10 



(6) Phase angle and ratio curves for typical current transformer. 

 .. 215. Current-transformer i-haracterist i 



The secondaries of practically all current transformers are 

 rated at 5 amp., reg.-mlless of the primary current raimu. For 

 example, a 2,000-amp. current transformer has a ratio of 400:1 

 and a 60-amp. Iran-former lias a ratio of 1 L> : 1. 



The eul-rerit transformer diflVrs from the ordinary <-oii-tant- 



poteiitial tranflformer in that its primary current i- d'-ln mined 



ly l>y the lo.-id on t he system and not by its own secondary 



load. It' ndary 1>< ..pen-circuited, a high voltage 



will . >roM the secondary 1 cause the large ratio of 



