In the two-wattmeter method of three phase power measurement, if the readings of two wattmeters are WI = 200 Watts and W2 = -200 Watts, then the operating power factor of the load is equal to:

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Question

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MPPGCL JE Electrical 28 April 2023 Shift 1 Official Paper

Answer 1

Two Wattmeter Method of Power Measurement

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The wattmeter meter readings are:

\(W_1=V_LI_Lcos(30+ϕ)\)

\(W_2=V_LI_Lcos(30-ϕ)\)

where, \(ϕ=tan^{-1}({\sqrt{3}(W_1-W_2)\over W_1+W_2})\)

The power factor is given by cosϕ.

Calculation:

Given, W₁ = 200 Watts and W₂ = -200 Watts

\(ϕ=tan^{-1}({\sqrt{3}(200-(-200))\over 200-200})=tan\space (\infty)\)

ϕ = 90°

Power factor = cos 90° = 0