

)ETAILED STUDY OF OPERATION WITH NORMAL LOAD 57 



Use of Diagram of the First Kind. The diagram of the first 

 id lends itself more rigorously than the other to the study of volt- 

 and current values when the motor is working at constant load; 

 it also applies equally well in the case where the impedance of the 

 icrator can be neglected. 



It is sufficient to cause the segments OA 2) O'A 2 , O"A 2 , O'"A 2 , (Fig. 

 t), representing the E.M.F. E 2 , to vary in inverse ratio with respect 

 the segments A 2 D, A 2 D', A 2 D", representing the active current 

 , in such manner that the product E 2 I W shall be constant and equal 

 to the given power PI. If, from each point, O, O', O", an arc of circle 



described, having for its radius the generator E.M.F. E\ , their respect- 

 ive intersections with the lines passing through D, D', D", D'" and 

 perpendicular to A 2 Y, determine the load-points AI, A'\, A'\, A'"\\ 

 and, consequently, the current-values / corresponding to the various 

 values of E 2 . This diagram also applies in the case where E\ varies 

 according to some given law. 



Predetermination of V-Curves. The preceding diagrams enable 

 these curves to be obtained by a simple graphical transformation, 

 without calculation. It is sufficient to measure, on the diagram itself, 

 the radial vectors for corresponding values of E.M.F. and current, 

 and to plot them as rectangular abscissae and ordinates. Each of the 

 power-lines of Fig. 28, for example, also gives a transformed curve 



