What actually you understand the meaning of power factor?

Answer 1

In a.c. circuits, there are two different 'types' of 'power': 'true power' and 'reactive power'.

'True power' describes the rate at which the energy supplied to a load is either lost to the surroundings through heat transfer or which does useful work (such as providing the output from a motor), and we measure this in watts.

'Reactive power' describes the rate at which energy is alternately stored in the load's magnetic or electric fields and, then, returned to the supply as the current increases and decreases every quarter-cycle, and we measure this in reactive volt amperes. Some books describe reactive power as the rate at which this energy 'sloshes back and forth, between the supply and the load's magnetic or electric fields', because it represents the movement of energy but not a loss of that energy!

For a given load, reactive power increases as the phase angle (the angle between the load current and the supply voltage) increases. Obviously, therefore, the greater a load's reactive power, the greater its apparent power.

The 'total' rate at which energy is moving in an a.c. circuit is the vector sum of true power and reactive power, and we call this the circuit's 'apparent power', expressed in volt amperes.

Power factor is simply the ratio between true power (expressed in watts) and apparent power (expressed in volt amperes) or the cosine of the phase angle.

Loads with low power factors (i.e. large phase angles) draw far more current than is necessary for the energy consumed from the supply. So, low power-factor loads require unecessarily-large supply conductors if higher-than-normal voltage drops and line losses are to be avoided and are, therefore, undesirable.