112 THE DESIGN OF STATIC TRANSFORMERS 



This may be done by splitting the coil up as shown in Fig. lit) 

 and connecting the primaries in series, the secondary coils 



Si and SB being connected in 

 series for one side of the three- 

 wire system and ,S'o mid N ( for 

 the other side ; or else Si and 

 Si may (as indicated in Fig. 70) 

 be connected in series for one 

 side, and S% and $3 for the other 

 side. 



Where the primary winding is 

 interposed between two second- 

 aries as shown in Fig. 71, it 

 becomes practicable to remedy 

 the unbalancing by connecting 

 Si and Si in series on one side and $2 and $ 3 in series on the 

 other side of the three-wire system, i.e., to connect the outside 

 secondary coil on one leg, in series with the inside secondary 

 on the other leg, as this tends to ensure the exact equality of 

 resistance and reactance in the two halves. 



FIG. 71. Arrangement of coils 

 in core-type transformer for 

 three-wire secondary. 



