650 



ELECTRICAL MEASUREMENTS 



ILLUSTRATION OF, THE USE OF A TWELVE-POINT SCHEDULE FOR 



THE ANALYSIS OF WAVES CONTAINING ONLY 



ODD HARMONICS 



FIG. 413. E.M.F. wave of small alternator. 



The e.m.f. wave of a small alternator is shown in Fig. 413. To analyze 

 this wave twelve equally spaced ordinates were measured; their values are 

 entered in the form below, 



y, = 8.50 

 yn = 8.70 



yi 4- yn = 17.20 y, + y, = 52.70 

 yi - yn = - 0.20 y s - yio = - 4-10 



0.30 



Sums 

 Differences 



Sums 

 Differences 



Calculation of AI and An 



(yi + yn) sin 15 = (17.2) 0.2588 = 

 (ys 4- y 9 ) sin 45 = (46.6) 0.7071 = 

 (y 6 4- yr ) sin 75 = (02.7) 0.9659 = 



M-L = 14-30 

 yio = 18.40 



0.00 

 20.00 



y, -f y, = 40.00 

 ys y = 5.40 



y = 82.26 

 y = 0.50 



ye 



(y a 4- yio) sin 30 



(y4 4- ys ) sin 60 



ye sin 90 



(52.7) 0.5000 = 

 (56.85) 0.8660 = 

 (52.25) 1.0000 = 



Sum 



(97. 965) t 

 (97. 833) 2 



196.798 = 

 = 52.055 



Difference 



(57. 555) 2 



0./52 = 

 = 0.022 



