122 



THE ELECTRIC ARC 



Transformer 



f VWWW 1, 



A. C. Supply 



loss would, therefore, be rather large on a no- volt circuit. 

 On circuits with higher voltage it would be correspondingly 

 smaller. 



An improved form of the converter which can be used 

 with currents as large as 700 amperes has recently been 

 brought out by the same inventor. 1 This is made of a 

 metallic envelope, through which the electrodes are in- 

 serted by way of porcelain tubes, the whole being sub- 

 jected to artificial cooling. It has been found possible to 

 use such a tube for a month without being reexhausted 

 while giving 200 kilowatts. This may well prove of value 



as a connecting link between 

 an alternating-current supply 

 system and direct-current 

 motors, such as are largely 

 used in. railway service. 



An ingenious modification 

 of this for use on a single- 

 phase circuit is described by 

 Weintraub. 2 This is shown 

 in Fig. 38. The tube. has three 

 terminals, A, A' and B. B 

 is a mercury terminal. The 

 others may be either mercury, 

 iron or carbon. Those shown 

 in the tube are carbon. C is 

 F IG 3 g an auxiliary terminal used in 



starting the arc. A and A' 



are connected to the terminals of an alternating-current 

 supply. E and F are coils having considerable inductance. 



1 Elec. World, 59, 628; 1912. 



2 Phil. Mag., (6), 7, 122; 1904. 



