14 



current machine, and as, owing to the 

 concentration of armature windings into 

 one coil, the limit of current as deter- 

 mined by heating will be reached sooner, 

 the current will be somewhat smaller 

 than half that of the direct-current ma- 

 chine, so that the output will be slightly 

 less. It must also be borne in mind that 

 a rectangular field with sharp corners 

 cannot be obtained. In consequence of 

 leakage and spreading of lines, the cor- 

 ners of the field will be more or less 

 rounded, as shown by dotted lines, and 

 this circumstance must lower the elec- 

 tromotive force beyond its theoretical 

 value. On these grounds it would there- 

 fore appear that this configuration of 

 field-magnets is not very advantageous, 

 but there are certain other considerations 

 which tend to modify this conclusion. 

 In actual machines it is not a single coil 

 which has to be dealt with, the active 

 wires in which occupy only a very nar- 

 row space, but wide coils covering a con- 

 siderable extent of surface on the arma- 

 ture ; there is also tlio question of self- 



