CHAPTER XL 

 GENERAL THEORY OF THE TRANSFORMER. 



114. Effects of coil resistances, magnetic leakage, and core 

 reluctance on the action of a transformer. The discussion of the 

 transformer which is given in Chapter X is based very largely 

 upon ideal conditions as explained in Art. 98, and the present 

 chapter is devoted to the discussion of the effects of coil resist- 

 ances, magnetic leakage, and core reluctance. These effects are 

 usually small, and their influence on each other (which is very 

 small) is ignored. That is, to say, the effect of each is here con- 

 sidered on the assumption that the transformer is otherwise ideal, 

 and the combined effect of all three is considered to be the sum 

 of the effects of each by itself. These effects may be summarized 

 in a general way as follows : 



Coil resistances do not effect the ideal current relation, namely, 

 I'II" = N"IN'\ but they do affect the ideal voltage rela- 

 tion, namely, E' JE" = N'/N" ; and the extent to which the coil 

 resistances affect the ideal voltage relation depends upon the 

 transformer load, the greater the load the more pronounced the 

 inequality E \E' > N' JN". 



Magnetic leakage does not * affect the ideal current relation of 

 a transformer, but it does affect the ideal voltage relation ; and 

 the greater the transformer load the more pronounced the 

 inequality E' IE" > N' / 'N", except when the receiving circuit is 

 like a condenser when the inequality is reversed. 



Core reluctance necessitates magnetizing current, and of course 

 the existence of magnetizing causes the ratio of primary current 

 to secondary current to differ from the inverse ratio of primary 

 to secondary turns. The extent to which the ideal current rela- 



*In the constant- current transformer, which is described in Art. 107, the magnetic 

 leakage is very large when the load is small, and in this case the magnetic leakage 

 does affect the current relation perceptibly. 



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