WAVE FORM 59 



Wave Form Potential Curve Between Brushes 



In determining the wave form of a direct current 

 machine the following method should be used: The 

 machine should be run at normal speed and voltage 

 and a pair of voltmeter leads, separated ..a distance 

 equal to the width of one commutator bar, placed on 

 the commutator under the center of one pole and moved 

 from bar to bar to the center of the next pole of like 

 polarity, the voltage at each step being read. In this 

 way the voltage between bars is obtained for a complete 

 cycle of 360 electrical degrees. 



The readings should be corrected for meter constants 

 and plotted as ordinates against the number of bars 

 as abscissae, and a sketch showing the position of the 

 poles should be made on the same sheet with the curve 

 obtained. 



Wave form on alternators is obtained by the use of 

 the oscillograph. 



