ABSTRACT
Power factor is a significant technical indicator of the power system, which is a basis of measure the inefficiency of electrical equipment. In the ac power system, load elements include resistance, inductance and capacitance. Phase between current through the resistor and the voltage across the resistor is same. Power dissipated in the resistor is from the energy conversion of coal, water and oil, which is called active power. Phase between current flowing through the inductor or capacitor and voltage across the inductor or capacitor is by 90°. Power formed on inductor or capacitor is from the magnetic field (inductive) and electric field (capacitive) power switching, no other energy conversion, so called reactive power. Power circuit can be divided into active power P, reactive power Q and apparent power S. The cosine of the phase difference between voltage and current (ψ) is called power factor, which means that the symbol cosψ. In value, the power factor is the active and apparent power ratio, i.e. cosψ = P/S.
