126 



Trails. Acad. Sci. of St. Louis. 



This is also true for the motor as is seen from fig. 11. The 

 poiuts do not lie as close to the line as in the case of the 

 dynamo since a tachometer was used to determine the speeds. 

 It will thus be evident that these straight lines will define the 

 dynamo and motor surfaces. It will therefore be necessary 

 to determine merely the characteristic of the machine. 



10 



12 



2 4 6 8 



Fig 12 



Series Motor Test. Characteristic Determined with Speed Equal to 1500. 



14 



The motor surface was also determined. See fi^. 11 and 



fig. 12. The surface is shown in fig. 18 — the lines DB, 



C'B' and C"B" being the ones determined. 



ni' 

 If we plot -g and i in order to get the constants of the 



surface in accordance with the method given on page 113, 

 we have the lines ab, be, and cd of fig. 13. The changes 

 in the direction of the line seem to indicate the points of 

 saturation of different parts of the magnetic circuit. This is 

 also seen to be even more pronounced in the case of the 

 motor in lines ef and fo; of fio-. 13. 



For a limited range the constants of another machine were de- 

 termined as is explained in connection with figs. 14, 15 and 16.* 



* The internal characteristic of a 1500 K. W. power generator was also 

 determined, and it was found that the relations could be expressed in the 

 above way with complete accuracy. 



