Use of capacitor and reactive power compensation:

In consumers such as electrخmotors, due to having a coiled wire, in addition to the active power that is taken from the network, some reactive power is also absorbed from the network, which does not play a role as the power that performs the work.
It only causes the reduction of the network power factor and also increases the cost of electricity consumption. Therefore, in order to improve the condition of the network and also to reduce the electricity consumption costs, it is better to compensate this reactive power in some way. Considering the nature of the coil in electric motors, which is a inductive, the best way to compensate is to use a capacitor whose impedance is the opposite of the inductance from the point of view of phasor.

But how much should be the amount of this capacitor?

Considering that the Inductance causes a phase difference between the voltage and the current or the same power factor, then the criterion for the capacitor value is the power factor.

The power factor (cos φ) in the case that the load is only ohmic, that is, the phase difference between the voltage and the current is zero, is equal to one, and for more inductive load, the phase difference will be more and the power factor will be less than one.

Therefore, when we want to compensate the reactive power, we actually want to make the power factor closer to one. If we consider power relationships, we will have:

Q(kvar)=P(kw).(tg φ2 – tg φ1)
φ1=Arc cos(P.F.1), φ2=Arc cos(P.F.2)

P.F.1: power factor 1
P.F.2: power factor 2

Electromotors or equipment that need to be compensated by capacitors can be compensated individually or in groups. Also, the electromotors can be started in the starting mode by using the compensating capacitor and then the capacitor is removed from the circuit.