Electrical Engineering ⇒ Topic : Disadvantages of Low Power Factor

Disadvantages of Low Power Factor

Since power consumed in AC circuits depends on the power factor, it plays an important role

                ...............(1)

            .............. (2)

From Eqs. (1) and (2), it is clear that for a fixed P and V_L, I_L is inversely proportional to power factor (cos Φ). So, the lower the power factor, the larger is the value of I_L. The larger current due to poor power factor has the following disadvantages:

(1) Large kVA rating of the equipment

The large electrical machinery is always rated in kVA.

                                 ........... (3)

From Eq. (3), kVA rating of the equipment is inversely proportional to the power factor.So, the lower the value of power factor, the higher is the kVA rating. The equipment will be larger in size and hence expensive.

(2) Greater conductor size

For transmission or distribution of a fixed amount of power at constant voltage, the conductor will have to carry more current at low power factor. This needs larger conductor size.

(3) Large copper loss

The high current at low p.f. causes more I²R loss.

(4) Poor voltage regulation

The large current at low power factor causes greater voltage drop in alternators, transformers,transmission lines, and also in the distribution systems.

(5) Reduced handling capacity of the system

Reactive component of current prevents full utilization of installed capacity