THE M.Tt'.RNATOR 111 



different phases. In Fig. 112, slots 1 and 2 contain both phase 

 .1 and phase C conductors; slots 3 and 4 contain phase A con- 

 ductors only; and slots 5 and 6 contain both phase A and phase 

 B conductors. Of this group, slots 3 and 4 contain phase A 

 conductors only. The fact that certain slots contain conductors 

 of different phases reduces slightly the inductance of the winding, 

 as has already been pointed out. 



Figure 114 shows a portion of a finished armature winding. 

 The end-connections, the binding down of the coil-ends, the 

 wooden slot wedges, and the ventilating ducts, are clearly shown. 



ALTERNATOR CONSTRUCTION 



56. Stator or Armature. The stator or stationary member of 

 the alternator is almost always the armature, the field structure 

 being the rotating member or rotor. When the machine is in 

 operation the armature iron is continuously cut by the flux of the 

 rotating field and must be laminated in order to reduce eddy- 

 current losses. In machines of small diameter, each lamination is 

 a single circular punching. 



High-speed turbo-alternators have armatures of small diam- 

 ond are usually built up of single circular stampings, as 

 shown in Fig. 115. The perforations back of the slots are ven- 

 tilating channels. Engine-driven alternators must rotate at com- 

 paratively low speeds and so must have a large number of poles, 

 and armatures of comparatively large diameter. The polepieces 

 are made up of laminations riveted together and are dovetailed 

 to the armature spider, as shown in Fig. 116. The armature 

 is built up of small overlapping segments, dove-tailed to the 

 frame of the machine in much the same manner as the armatures 



-ine-driven, direct-current generators are assembled 

 Vol.1 pt that in the alternator the anna- 



tun- laminations are a part of the stationary member. Figure 

 boW8 the general construction of such an alternator. The 

 frame it-elf i- usually a hollow box casting. Thi the neces- 



sary mechanical stiffness, with the minimum weight, and the 

 space within the frame allow- a five circulation of air for venti- 

 lating purposes. Figure 1 17 shows the complete armature of an 

 ermine-driven generator. The ventilating ducts and the bracing 

 of the coil end- -hould be particularly noted. 



