PARTS OF A DYNAMO-ELECTRIC MACHINE 



75 



shall not discuss it further except in connection with the 

 Thomson-Houston arc generator which illustrates another 

 type of winding. 



The drum winding is not easy to show by a diagram 

 however and so we shall, in analyzing the action of a drum 

 winding, often picture the drum winding as a ring winding. 

 The ring winding is easier to represent and the deductions 

 we make regarding its action apply equally well to the drum 

 winding. 



FIG. 38. View of a Ring- wound Armature (Early Type). 



Wheeler Co. 



Crocker- 



Drum Winding. The drum winding is distinguished 

 by the fact that all of the armature conductors are on the 

 outside surface of the armature core; the coils do not thread 

 through the inside of the armature as they do in the ring 

 winding. The drum winding does not contain as much 

 inactive vrire, therefore, as the ring winding, also the opera- 

 tion of winding the armature, is much more easily accom- 

 plished with the drum than with the ring type. These 

 are two of the advantages which make the drum winding 

 so universally used. A typical drum wound armature 

 is shown in Fig. 39. This illustrates a medium sized drum 



