216 



ELEMENTS OF ELECTRICAL ENGINEERING. 



This arrester is made by the General Electric Company. It is 

 suitable for direct current circuits only, and, being compact and 

 enclosed, it is specially suitable for pro- 

 tecting the motors on street cars. The 

 spark gap in this arrester is between the 

 ends of two short brass rods which are 

 shown attached to a porcelain lug on the 

 inside of the cover in Fig. 130. A carbon 

 rod resistance is connected in series with 

 this spark gap, and the winding of the 

 blow-out magnet is connected as a shunt 

 around the whole or a portion of this car- 

 bon resistance. The magnet blows the 

 arc out through a hole (shown in Fig. 

 131) in the porcelain lug and cover. Fig. 132. 



Fig. 132 shows the details of the arrester and the manner in 

 which it is connected to the line and to the ground. Fig. 1 3 3 

 shows four of these arresters connected to two pairs of feeders, 

 and two additional arresters connected to the generator mains. 



Buses 



Reactance 

 Co//s 



feeder 

 Fig. 133. 



feecfef 



Fig. 134 shows a Wurts alternating current lightning ar- 

 rester manufactured by the Westinghouse Company. It con- 

 sists simply of seven massive brass cylinders held in a porcelain 

 clamp, and presents seven spark gaps in series between the end 

 cylinders which are connected to the terminals G and L. The, 

 point L is connected to the line and the point G to ground. Fig. 



