86 



ALTERNATING CURRENTS 



field-poles, as the wires would roll over each other. For this reason, 

 the usual form of field winding consists of thin strips of copper 

 wound on edge in one or two layers. This kind of winding is known 



- STRIP 

 WINDING 



FIGS. 69 and 70. Methods of supporting Field-poles. 



as edge-strip winding, and is shown diagrammatically in Fig. 70. 

 Besides being mechanically strong, it possesses the further advantage 

 of rapidly conducting the heat to the outside of the coil, and so 



FIG. 71. Types of Laminated Pole-shoes. 



maintaining it at a uniform temperature, thereby preventing excessive 

 rises of temperature in the interior of the coil. 



In order to prevent excessive eddy-current loss in the ends of the 



FIG. 72. Showing construction of Skewed Pole-shoe. 



pole-pieces, these are frequently laminated. In Fig. 71 are shown 

 various ways of securing the laminated pole-shoes to the field-cores. 

 For the purpose of securing a smooth wave-shape forming a close 



