CHAPTER III 



THE ARMATURE FRAME 



A FRAME is required for the mechanical support of the armature 

 core plates. When the armature is the rotor, this support 

 generally consists of an internal hub or spider intermediate 

 between the shaft and the laminations. The laminations are 

 compressed -between flanges secured at each end of the spider. 

 These flanges are often extended to form a support for the end 

 connections of the armature winding. 



Fig. 52 shows the armature spider of a 10-pole, 300 k.w., 

 100 r.p.m. generator. In this case there are six spider arms, 

 and two recesses per arm are provided for bolts which pass 

 through holes in lugs projecting inwardly from the armature 

 core plates. Fig. 53 shows one core plate in place on this 

 spider. In Fig. 54, the end flanges are shown in place on the 

 spider, the core plates being omitted. A similar construction is 

 shown in Fig. 55 ; this is for a 6-pole, 200 k.w., 135 r.p.m. 

 machine. The spider has eleven arms, and receives only one 

 lug per arm. Thus, instead of an integral number of core-plate 

 segments per complete disc (as in Figs. 52 and 53, where there 

 were six complete segments per disc), there are, in the case 

 of Fig. 55, five and a half segments per disc, so that, in 

 assembling the core-plate segments, the last half of the sixth 

 segment laps over into the next layer. In both cases the core 

 plates are secured by bolts passing through rectangular lugs, as 

 seen in Figs. 54 and 55. In the case illustrated in Fig. 56, 

 however, which shows the spider of a 6-pole, 250 k.w., 320 r.p.m. 

 generator, the core-plate segments are retained by dovetailed lugs 

 engaging in corresponding recesses in the ends of the spider arms. 

 In this case, the bolts compressing the core plates between the 

 end flanges are entirely below and separate from the armature 

 core. In Figs. 57 and 58 are given photographs of spiders of 



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