Question

The meter constant of a 230 V, 10 A watt-hour meter is 1800 revolutions per kWh. The meter is tested at half load and rated voltage and unity power factor. The meter is found to make 80 revolutions in 138 seconds. The meter error at half load is ______ % fast.

• A. 0.817

Answer 1

The correct option is A 0.817
Actual energy consumed at half load during 138 sec

$=VIcos\varphi \times t\times {10}^{-3}$

$=230\times 5\times 1\times \frac{138}{3600}\times {10}^{-3}=44.08\times {10}^{-3}kWh$

$Energyrecorded=\frac{Numberofrevolutionsmade}{Revolutions/kWh}$

$=\frac{80}{1800}=44.44\times {10}^{-3}kWh$

$\therefore \%error=\frac{44.44-44.08}{44.08}\times 100=0.817\%fast$