Question #201800

An electrical load operates at 240 V rms The load absorbs an average of 8 Kw at lagging power factor of 0.9 The load impedance is:

Â Select one:

Â A 5.04 L 45 57 Â°Î©

Â B 3.6 L 60 Â°Î©

Â C 5.76 L 36.87 Â°Î©

Â D 4.32 L 53.13 Â°Î©

Â E 6.48 L 25.84 Â°Î©

Expert's answer

Average power, PÂ "= 8KW"

ButÂ "P=\/S\/ cos \\theta"

Given power factorÂ "cos \\theta=0.9"

"=sin \\theta=\\sqrt{1-cos^2\\theta}"

"=sin \\theta=\\sqrt{1-0.9^2}=\\sqrt{0.19}=0.44"

"P=\/S\/ cos \\theta"

"8KW=\/S\/*0.9"

"\/S\/=\\frac{8000}{0.9}=8888.89"

Reactive power, QÂ "=\/S\/ sin\\theta"Â VAR

"Q=8888.89(0.44)=3910.72"Â VAR

"S=P+jQ"

"S=8000+j3910.72"

"S=8+j3.91"Â KVA

Impedence, Z "\\frac{S}{I^2}=4.32 \\angle 53.13 \u00b0\u03a9"

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