Electrical Engineering ⇒ Topic : 3Voltmeter Method of Determining Phase Angle

Daniel
 
3Voltmeter Method of Determining Phase Angle It is sometimes very convenient to determine the phase angle between two voltages V_{12 }and V_{23}with no equipment other than 3 a.c. voltmeters connected as shown in Fig. a (i). The method may be used to determine the phase angles between line voltages of 3phase circuits by connecting the lines directly to the junctions of the voltmeter leads as shown in Fig. a (ii). figure (a) By Kirchhoff's voltage law, the phasor sum of the three voltmeter readings is zero. We can thus obtain the graphical solution as shown in Fig.(B). First, the base line is drawn proportional in length to one of the voltmeter readings, in this case V_{31}. Next two arcs are drawn ; one having a radius originating at point 1 and proportional in length to V_{12}, and the other having a radius originating at point 3 and proportional in length to V_{23}. The intersection of the two arcs becomes point 2 and locates the ends of phasors V_{12 }and V_{23}. From familiar principles of trigonometry, we have
figure (b)  
 
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