198 



Mr. W. G. Rhodes on 



coincidence. The point F is obviously got by taking OE/ 

 equal to E and through E/ drawing E^P parallel to OT. 



Fig. 4. 



The resulting parallelogram OP'T^ shows that the generator 

 E.M.F. is in phase with the current. 



19. Suppose now that the excitation of the generator field 

 is kept constant while that of the motor is varied. 



When the motor excitation is small, as Oe (fig. 4), we see 

 that the current leads over the motor E.M.F. and lags 

 behind the generator E.M.F. 



When e exactly opposes c, the latter lags behind E. 



When E and c are in phase (minimum current),, c lags 

 behind e. 



When e is still further increased, as Oe 1 , c leads before E 

 and lags behind e. 



