TRANSFORMERS 



321 



maximum and is in opposition to the impressed voltage, and so 

 gives the minimum load voltage. 



In Fig. 305 OP is the impressed voltage or line voltage, OSi is the 

 maximum secondary induced voltage and SiP is the load voltage. 



The load current of the circuit flows in the secondary, and 

 there must also be a load current in the primary of equal and 

 opposite m.m.f . as in the ordinary transformer. 



/Secondary Coll S 



-Primary Coil P 



FIG. 301. FIG. 302. 



Single-phase induction regulator. 



FIG. 303. 



When the movable core is turned through an angle 6, Fig. 302, 

 only part of the primary flux passes through the secondary and 

 the secondary voltage is reduced approximately in the ratio 

 1 : cos 6, but is still in opposition to the line voltage. The load 

 voltage is represented by $ 2 P, Fig. 305. 



Secondary 



Line 



Load 



8584 



FTG. 304. 



S 2 Si 



FIG. 305. 



With the primary coil at right angles to the secondary coil, 

 Fig. 303, none of the primary flux passes through S and there is 

 no secondary induced voltage. 



When the core is turned through 180 degrees the secondary 

 voltage is again maximum, but is in phase with the impressed 

 voltage and so raises the load voltage to S^P. Thus the total 

 variation of the load voltage is from SiP to S*P and is equal to 

 twice the maximum secondary voltage. 



