SYNCHRONOUS GENERATORS 



333 



off the heat generated. Thin, coil-shaped copper pipe is embedded 

 in the lower bearing half just below the surface of the babbitt and 

 cooling water is forced through the coil. If the water wheel is 

 of the overhung type, the size of the bearing nearest the wheel must 

 be of sufficient size to take care of the extra weight. Whether the 

 water thrust is balanced or not must also be considered. 



With vertical units the present practice is to support the 



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O . CD C 

 ODD 



FIG. 195. Typical Design of Modern Vertical Generator with Direct-con- 

 nected Exciter. 



revolving element of the entire unit from a thrust bearing mounted 

 on top of the generator frame. Two guide bearings are usually 

 provided with the generators, one in the upper bracket directly 

 below the thrust bearing, and the other one supported in a bracket 

 below the revolving field (Fig. 195). Generally, one guide bearing 

 is provided in connection with the water wheel. This is usually 

 a babbitted bearing, although sometimes the lining is of lignum 

 vitae. In case of very low-speed machines, where it is possible to 



