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Power Factor Correction Gonzalo Cuevas Ezquerra

IndexWhat is the Power Factor?Power Factor diagramReactive powerPractical values of power factorWhy improve the power factor?How to improve the power factor?Where to install the banks?22What is the Power Factor?33Power Factor diagramCurrent vector diagram

Power vector diagram4

Reactive powerCreated by the circulation of current in coilsProduces the worst possible conditions of voltage dropDrops the power factorCause losses in transmission and distribution systems5Reactive Power Reduction

Practical values of power factorEquipment and appliancescos Common induction motorloaded at0%25%50%75%100%0.170.550.730.800.85Incandescent lampsFluorescent lamps (uncompensated)Fluorescent lamps (compensated)Discharge lamps1.00.50.930.4 to 0.66Practical values of power factorEquipment and appliancescos Ovens using resistance elementsInduction heating ovens (compensated)Dielectric type heating ovens1.00.850.85Resistance-type soldering machinesFixed 1-phase arc-welding setArc-welding motor-generating setArc-welding transformer-rectifier set0.8 to 0.90.50.7 to 0.90.7 to 0.8Arc furnace0.87Why improve the power factor?Reduction in the cost of electricityTechnical/economic optimization:Reduction of cable sizeReduction of losses in cablesReduction of voltage dropIncrease in available power8Reduction in the cost of electricityThe power supply authority delivers reactive energy for free:If is less than 40% of the active energy (PF=0,928) for maximum 16h a day during the most-heavily loaded periodWithout limitation during light-load periodsAgainst those advantages, consumers must balance the cost of purchasing, installing and maintaining the power factor correction equipment9Technical/economic optimizationReduction of cable size:

Reduction of losses in cables:Reduction of the current by 10% reduce losses by 20%Reduction of voltage drop:Reducing the reactive current we reduce the voltage dropIncrease in available power:Improving the PF current reducedmore load can be added10Multiplying factor for the cross-sectional area of the cable core(s)11.251.672.5 cos 10.80.60.4How to improve the power factor?If we add a bank of shunt capacitors to the load, the capacitive current, which is in direct phase opposition to the load reactive current, cancel the load reactive power.

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ConnectionsFixed capacitors: Manual, semi-automatic or direct connection to an applianceApplied at the terminals of inductive devices, busbars of small motors, with constant loadsAutomatic capacitor banks:Used in places where the active-power or reactive-power variations are largeDivided into sections controlled by contactorsThe size of the bank changes according to our preferences1213

Where to install the banks?Global compensationFor loads continuous and stablesReduces tariff penalties for excessive consumption of kvarsReduces apparent power kVA demandRelieves the supply transformer14

Where to install the banks?Compensation by sectorFor extensive installationsReduces tariff penalties for excessive consumption of kvarsReduces apparent power kVA demandRelieves the supply transformerReduces the size of the cables which supply the local distribution15

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