Electrical Engineering ⇒ Topic : Power Factor Improvement

Power Factor Improvement

The low power factor is mainly due to the fact that most of the power loads (e.g., induction motors etc.) are inductive in nature and, therefore, take lagging currents. In order to improve the power factor, some device taking leading current should be connected in parallel with the load. One of such devices can be a capacitor. The capacitor draws a leading cun-ent and partly or completely neutralises the lagging reactive component of load current. This raises the power factor of the load.

Illustration. To illustrate the power factor improvement by a capacitor, consider a *single phase load taking lagging current I at a pf. of cos Φ1 as shown in Fig.a(i). The capacitor C is connected in parallel with the load and draws current I_c which leads the supply voltage by 90⁰ .The resulting line current P is the phasor sum of I and I_c and its angle of lag is Φ₂ as shown in the phasor diagram in Fig.(iii). It is clear that Φ₂ is less than Φ₁, so that cos Φ₂ is greater than cos Φ₁. Hence, the power factor of the load is  increased.

                                                                                     figure 

The following points are worth nothing :

(1)The circuit current T after p f correction is less than the original circuit current I.

(2)The active or wattful component remains the same before and after pf correction because only the lagging reactive component of load is reduced by the capacitor i. e.