318 



THE ROTARY CONVERTER. 



The ratios of direct and alternating currents and 

 voltages may be conveniently tabulated in the following 



manner : 



Magnetisation Curve or Open-Circuit Characteristic of a Rotary 

 Converter. In order to ascertain the magnetic properties 

 of the converter, and the most suitable excitation, this 

 curve should be obtained, as in the case of a direct or 

 alternating-current generator. 



If it is possible to drive the machine by external 

 means, the test should be carried out exactly as described 

 in Experiment XXXIV. for an alternator. The machine is 

 driven by a belt or coupling at a constant speed, and the 

 excitation, which should be supplied from an external 



FIG. 158. DIAGRAM OF CONNECTIONS. 



source of direct current, is gradually increased from zero 

 to a value considerably above the normal. Voltmeters 

 should be connected to both alternating and direct sides 

 of the armature, and must be read for each value of the 

 excitation. After a similar series of readings have been 

 taken with decreasing values of the exciting current, the 

 mean curve should be .plotted with amperes or ampere- 

 turns horizontal, and direct and alternating voltages 

 vertical. 



