CONVERTERS 



371 



In a series-wound armature the total number of coils must be 

 divisible by the number of phases and in a multiple-wound arma- 

 ture the number of coils per pair of poles must be divisible by the 

 number of phases. 



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fa) Delta Primary Star Secondary 



(2) <D CD 



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Converter 1 







Delta Primary Double Delta Secondary 







( C ) Delta Primary Ring Secondary 

 FIG. 352. Six-phase power from three-phase circuits. 



Six-phase converters are operated from three-phase circuits. 

 Three methods of connecting the supply transformers are shown 

 in Fig. 352. 



234. Field Excitation. The fields of a rotary converter are 

 excited by direct current, usually supplied by an exciter mounted 



