CONVERSION OF ALTERNATING CURRENT. 



173 



of the tube at either of the electrodes A or A f ', that is to say, 

 the two electrodes A and A' act like valves. Two inductance 

 (reactance) coils, E and F are inserted as shown in the figure. 

 The effect of these coils 

 is as follows : Consider 

 the flow of current rep- 

 resented by the full -line 

 arrows. This current VVVV\AAAAA/ ( 1 



passes through Coil E. Secondary 



As this half-wave of 

 alternating current dies 

 away, the momentum of 4 

 the current in the in- j 

 ductance coil E causes 

 the current to continue 

 to circulate in the short 

 circuit DEA'B^nd thus 

 maintain an outflowing 

 current at B until the 

 reverse wave of alter- 

 nating current begins to 

 flow into the tube at A' . 

 The continued opera- 

 tion of the rectifier re- 

 quires that the outflow- 

 ing current at B never 

 become zero. 



Comparison of methods (ti) and (c], The motor- generator and 

 the synchronous converter are the only devices which are avail- 

 able for heavy service in the conversion of alternating current 

 into direct current.* The synchronous converter has a higher 



*The practical possibilities of the mercury-arc rectifier are not as yet fully 

 established. At the present time this rectifyer is built in sizes large enough to deliver 

 thirty or forty amperes of direct current with a loss of about 14 volts in the mercury arc. 

 The mercury-arc rectifier is suitable for any voltage up to 10,000 volts or more. 



00000 



F 



Fig. 147. 



