328 



SYNCHRONOUS MACHINES. 



[Exp. 



tation characteristics as for a synchronous motor (21, 23, 24, 

 Exp. lo-A). 



1 8. Full-load Excitation Test. Repeat the test, keeping the 

 direct current constant at rated full-load value, or other selected 

 value. 



19. Load Run; Excitation Constant. With constant excita- 

 tion* (for which separate excitation may be convenient), vary the 

 D.C. load and take simultaneous readings of all instruments. 

 Make runs with over-excitation, normal-excitation and under- 

 excitation. 



20. Tests with Series Reactance. Place a reactance in series 

 with each line (for a single-phase converter, reactance in one line 

 is sufficient")") and repeat the preceding tests. 



Read all instruments, as shown in Fig. 2; also read voltage 



FIG. 2. Connections for operating a synchronous converter. 



drop around the coil X, which should be so designed that the 

 drop does not exceed, say, 25 per cent, of the terminal voltage. 



Measure the resistance and reactance of the coil, plotting results 

 as in Fig. 7, Exp. 5~B. 



21. Results. Show all results by curves and compare curves 

 with and without series reactance, particularly the curves show- 

 ing voltage variations. Efficiencies are computed from input 

 and output. Construct diagrams, as Figs. 3, 4, 5, Exp. 3-B. 



* As a modification, with the converter self-excited, leave the field 

 rheostat in one position. 



t When supplied from independent transformers, 2 reactances are suffi- 

 cient for a 2-phase converter; 3 reactances, for a 6-phase converter. 



