Non-linear loads, such as rectifiers, distort the current drawn from the system. Linear loads with low power factor (such as induction motors) can be corrected with a passive network of capacitors or inductors. Power-factor correction increases the power factor of a load, improving efficiency for the distribution system to which it is attached. Because of the costs of larger equipment and wasted energy, electrical utilities will usually charge a higher cost to industrial or commercial customers where there is a low power factor. The higher currents increase the energy lost in the distribution system, and require larger wires and other equipment. In an electric power system, a load with a low power factor draws more current than a load with a high power factor for the same amount of useful power transferred. A negative power factor occurs when the device (which is normally the load) generates power, which then flows back towards the source. Due to energy stored in the load and returned to the source, or due to a non-linear load that distorts the wave shape of the current drawn from the source, the apparent power may be greater than the real power. Apparent power is the product of RMS current and voltage. Real power is the instantaneous product of voltage and current and represents the capacity of the electricity for performing work. A power factor of less than one indicates the voltage and current are not in phase, reducing the average product of the two. In electrical engineering, the power factor of an AC electrical power system is defined as the ratio of the real power absorbed by the load to the apparent power flowing in the circuit, and is a dimensionless number in the closed interval of −1 to 1. (2π f (Hz)× V L-L(V) 2) Calculation with line to neutral voltageĬ (F) = 1000 × Q c (kVAR) / (3×2π f (Hz)× V L-N(V) 2) Power factor definition (2π f (Hz)× V (V) 2) Three phase circuit calculationįor three phase with balanced loads: Calculation with line to line voltage Q c (kVAR) = Q (kVAR) - Q corrected (kVAR) Q corrected (kVAR) = √( S corrected (kVA) 2 - P (kW) 2) S corrected (kVA) = P (kW) / PF corrected Power factor correction capacitor's capacitance calculation: The power factor correction calculation assumes inductive load. The power factor calculation does not distinguish between leading and lagging power factors. The power factor correction capacitor should be connected in parallel to each phase load.
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