62 



ARMATURE CONSTRUCTION 



discs, thus providing inlets for the air from the outside to the 

 vertical ventilating ducts. Except in the case of the very largest 

 of continuous-current turbo-generators, a similar difficulty is 

 encountered. In the case of the design for a 750 k.w. generator 

 at 1500 r.p.m., the difficulty is met as shown in Fig. 64. 



FIG. 58. Photograph of Armature Spider of large Generator. Dick, Kerr & Co. 



Fig. 65 shows a few alternative methods of keying the lamina- 

 tions to the spider arms. 



For external stationary armatures, the punchings may be 

 assembled in skeleton castings of a variety of designs, of which a 

 few typical instances are given in Figs. 66 to 73. 



Fig. 66 shows the casting for the frame of a moderate size 

 stationary armature. In the front of the frame is seen one 

 of the end flanges cast on to the frame itself. The armature 



