INTRODUCTORY 1 



machines, a chart is given in Fig. 8 which shows an outline 

 sketch of the five common classes of dynamo machinery, with 

 the parts which comprise the stator and rotor tabulated in 

 columns. 



In the outline sketches the armature is marked A and the 

 field system F. Also in the columns designated stator and rotor, 

 the armature system, wherever it occurs, is entered in heavy type. 

 It is with the parts marked A, and entered in heavy type, that 

 the present work deals. 



In all of the cases shown in Fig. 8 the stator is external to 

 the rotor, and the rotor revolves inside the stator. 



FIG. 7. Wound Slip-ring Rotor. Alioth Co. 



There have been a few 'machines built which depart from this 

 practice, but these are so very rare and old that they are not 

 included here. 



Under Class I. Continuous - Current Generators some 

 machines were once built by Messrs Siemens & Halske, having a 

 revolving armature with stationary poles at the interior of the 

 armature. The armature was gramme ring wound, the conductors 

 on the outside of the periphery forming the commutator on which 

 the brushes pressed. 



Were this type of machine used now to any extent, we should 

 have inserted it in the chart of Fig. 8 as a type B continuous 

 current machine of the inner pole type ; the armature, however, 

 would still be the rotor. 



In Class III. Alternators some machines have been built 

 by the Westinghouse Co., having a stationary armature with 



