202 



ALTEBNATOBS. 



regulating resistance. Connect the armature to an adjus- 

 able load resistance in series with an ammeter and switch. 

 Connect a voltmeter to the alternator terminals. 



Before exciting the alternator, close the switch in the 

 load circuit and make E l as low as possible. Run the 

 alternator at normal speed and then increase the excitation 

 slowly until the full load current is reached. Maintain the 

 speed constant and increase the excitation step by step, at the 



O -2 -4 -6 -8 1-O 1-2 1-4 1-6 1'8 2'O 22 2'4 2'6 



Amperes, excitation. 



PIG. 94. MAGNETISATION CUBVE WITH LOAD. 

 Load current - 20 amps. 



same time increasing the resistance in the load circuit so as 

 to maintain the load current at the same value as before. 

 In each case take simultaneous readings of voltage and 

 exciting current. Enter the readings in tabular form as in 

 the preceding experiment. The results are then to be plotted 

 to give the full -load magnetisation curve with volts vertically 

 and exciting current horizontally, as in the case of the no-load 

 curve of the previous experiment. 



