The overall power factor is defined as the cosine of the angle between the phase voltage and phase current. In AC circuits, the power factor is also defined as the ratio of the real power flowing to the load to the apparent power in the circuit. Hence power factor can be defined as watts to volt-amperes.
It is also defined as the ratio of resistance to the impedance of the circuit. So, by increasing resistance, the power factor can be increased. But due to power losses practically it is not used. Typically, the capacitor is used for power factor improvement purposes.
The Current “I” is inversely proportional to CosФ i.e., the Power Factor. In other words, when the power factor increases, the Current Decreases, and when Power Factor decreases Current Increases.
Disadvantages of low power factor:
Large kVA rating of the equipment:
The power factor is inversely proportional to the kVA. CosФ = kW / kVA. The Lower the Power factor, the larger the kVA rating of Machines also, the larger the kVA rating of Machines, The larger the Size of Machines and Larger the size of Machines, The larger the Cost of machines.
Greater conductor size:
In case of a low power factor, the current will be increased, thus, to transmit this high current, we need a larger size conductor. Also, the cost of a large size of conductor will be increased.
Large copper losses or line losses:
Line Losses are directly proportional to the squire of the electric current. the larger the current, the greater the line losses.
Poor voltage regulation and larger voltage drop:
In case of a Low Power factor, the Current will be increased. So, the Larger the current, the Larger the Voltage Drop. In case of a Low Power Factor (lagging Power factor), there would be a large voltage drop which causes low voltage regulation.
The reduced handling capacity of the system or Low Efficiency:
In case of low Power Factor, there would be a large voltage drop and large line losses and this will cause the system or equipment efficiency too low.
The cost of station and distribution equipment is more for a given load:
The electrical Power supply Company imposes a penalty of power factor below 0.95 lagging in the Electric power bill.