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 Ic which leads the supply voltage by 900 .The resulting line current P is the phasor sum of I and Ic 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.
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.
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