CH. XIII] CANDLE-POWER OF ARC LAMPS 



CANDLE-POWER OF ARC LAMPS 



553 



754. A number of measurements of the candle-power of arc 

 lamps have been made, partly in the Physical Laboratory at 

 Cornell University, and partly in the Illuminating Engineering 

 Laboratory of the General Electric Company at Schenectady. 

 The experiments made at Cornell were for the higher currents and 

 were made primarily to ascertain the efficiency of the mercury arc 

 rectifier and the power consumption with different forms of ballast 

 ( 754a). 



FIG. 301. 



CARBONS IN THE CORRECT RELATIVE POSITION FOR BOTH DIRECT 

 AND ALTERNATING CURRENTS. 



A Inclined carbons in the correct position for alternating current. 



B Inclined carbons in the correct position for direct current. 



C Carbons at right angles in the correct position for either direct or 

 alternating current. Direct current is indicated. 



D Carbons arranged in a V-shaped position. For this position alternating 

 current only is employed; and the crater on each carbon contributes to the 

 light. The V may be either in a vertical or in a horizontal plane. The ver- 

 tical arrangement is the more common. 



755. Variation of Candle-Power with current. Candle-power 

 measurements were made in the horizontal direction, that is, along 

 the axis of the lantern, using different currents and with both the 

 right-angle and the inclined-carbon arrangements. Great care 

 was taken to hold the position of the electrodes and craters as 

 shown in fig. 301, as these positions furnish the greatest amount of 

 light. With direct current especially, it is necessary that the crater 



754a. The results of the Schenectady tests were published in the Electrical 

 World, Oct. 13, 1911. 



