214 



ALTERNATORS. 



EXPERIMENT XXXVI. DETERMINATION OF THE 

 CHARACTERISTIC OF AN ALTERNATOR. 



DIAGRAM OF CONNECTIONS. 



S 



M ! M% Source of direct current. 



O Alternator armature. 



F Alternator field windings. 



R l Non-inductive resistance for varying load. 



jR 2 Resistance for maintaining excitation constant. 



A l Ammeter for measuring load current. 



A z Ammeter for measuring exciting current. 



V Voltmeter for reading alternator voltage. 



S Switch for breaking main circuit. 



Instructions. Excite the fields of the alternator from a 

 source of direct current in series with a regulating resistance 

 and ammeter. 



Connect the armature to a variable non-inductive resis- 

 tance in series with an ammeter and switch. Connect a 

 voltmeter to the armature terminals. 



Run the alternator at constant speed and maintain the 

 excitation (read on ammeter A 2 ) constant throughout the 

 experiment. 



Take readings of armature voltage and current, first 

 with the switch S open, and then for gradually increasing 

 values of the load up to the maximum output. Repeat the 

 readings while decreasing the current by similar steps. 



Enter the results in tabular form as shown below, and 

 plot a curve in which voltage is measured vertically and 

 current horizontally. 



