Electrical Engineering ⇒ Topic : Calculations of Power Factor Correction

Lalan
 
Calculations of Power Factor Correction Consider an inductive load taking a lagging current I at a power factor cos Φ. In order to improve the power factor of this circuit, the remedy is to connect such an equipment in parallel with the load which takes a leading reactive component and partly cancels the lagging reactive component of the load. Fig. a (i) shows a capacitor connected across the load. The capacitor takes a current I_{c},which leads the supply voltage V by 90°. The current I_{c} partly cancels the lagging reactive component of the load current as shown in the phasor diagram in Fig.a (ii). The resultant circuit current becomes I and its angle of lag is Φ_{2}. It is clear that Φ_{2} is less than Φ_{1} so that new p.f. cos Φ_{2 }is more than the previous p.f. cos Φ_{1}.
Figure (a) Power triangle. The power factor correction can also be illustrated from power triangle. Thus referring to Fig. (b), the power triangle OAB is for the power factor cos Φ_{1} whereas power triangle OAC is for the improved power factor cosΦ2. It may be seen that active power (OA) does not change with power factor improvement. However, the lagging kVAR of the load is reduced by the p.f. correction equipment, thus improving the p.f. to cosΦ_{2}. Leading kVAR supplied by p.f. correction equipment
figure (b)
Knowing the leading kVAR supplied by the p.f. correction equipment, the desired results can be obtained. The p.f. of an electric system is very important to power companies and large industries because p.f. determines how efficiently the power distribution equipment (e.g. transformer, power lines etc.) is used  
 
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