Electrical Engineering ⇒ Topic : Significance of Power Factor

Lalan
 
Significance of Power Factor The apparent power S drawn by a circuit has two components viz (i) true power P and (ii) reactive power Q. True power component should be as large as possible because it this component which does the useful work in the circuit. This is possible if the reactive power component is small. As seen from the power triangle in Fig.(a), the smaller the phase angle Φ (i.e. greater the power factor cos Φ, the smaller is the reactive power component. Thus when Φ = 0 (i.e., cos Φ = 1),
figure (a) the reactive power component is zero and the true power is equal to the apparent power (P = VI cos Φ = VI cos 0^{0} = VI= S). This means the whole of apparent power drawn by the circuit is being utilised by it. Thus power factor of a circuit is a measure of its effectiveness in *utilising the apparent power drawn by it. The greater the power factor of a circuit, the greater is its ability to utilise the apparent power. Thus 0.5 p.f. (i.e. 50 p.f.) of a circuit means that it will utilise only 50% of the apparent power whereas 0.8 p.f. would mean 80% utilisation of apparent power. For this reason, we wish the power factor of the circuit to be as near to 1 as possible. True power, P = VI cos Φ watts (W) Apparent power, S = I voltamperes (VA) Reactive power, Q = VI sin Φ voltamperes reactive (VAR)  
 
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