Question

The line to line input voltage to the 3-phase 50 Hz, AC circuit shown in figure is 100 V rms. Assuming that the phase sequence is RYB the wattmeter would read.

• A. $W_1=886Wand{W}_2=896W$
• B. $W_1=500Wand{W}_2=500W$
• C. $W_1=0,Wand{W}_2=1000W$
• D. $W_1=250Wand{W}_2=750W$

Answer 1

The correct option is C $W_1=0,Wand{W}_2=1000W$

$V_L=100V$

$I_L=I_p=\frac{V_p}{Z}=\frac{100/\sqrt{3}}{5\times \angle {60}^{\circ }}$

$=\frac{20}{\sqrt{3}}\angle -{60}^{\circ }A$

$W_1=V_L{I}_{L}cos({30}^{\circ }-\varphi )$

$=100\times \frac{20}{\sqrt{3}}cos\{{30}^{\circ }-(-{60}^{\circ }\left)\right\}$

$=\frac{2000}{\sqrt{3}}cos{90}^{\circ }=0W$

$W_2=V_L{I}_{L}cos({30}^{\circ }+\varphi )$

$=100\times \frac{20}{\sqrt{3}}cos({30}^{\circ }-{60}^{\circ })=1000W$