


Power Factor Calculations.Power factor is the ratio between the KW and the KVA drawn by an electrical load where the KW is the actual load power and the KVA is the apparent load power. It is a measure of how effectively the current is being converted into useful work output and more particularly is a good indicator of the effect of the load current on the efficiency of the supply system. There are two types of power factor, displacement power factor and distortion power factor. Only displacement power factor can be corrected by the addition of capacitors.
For a given power factor and KVA (line current) the KVAR (reactive current) can be calculated as the KVA times the sine of the angle between the KVA and KW. Three phase calculations:KVA = Line Current x Line Voltage x sqrt(3)
/ 1000 KW = KVA x pf = V x I x sqrt(3) x pf Single phase calculations:KVA = Line Current x phase Voltage /1000 KW = KVA x pf = V x I x sqrt(3) x pf
To calculate the correction to correct a load to unity, measure the KVA and the displacement power factor, calculate the KVAR as above and you have the required correcion. To calculate the correction from a known pf to a target pf, first calculate the KVAR in the load at the known power factor, than calculate the KVAR in the load for the target power factor and the required correction is the difference between the two. i.e. Measured Load Conditions:
(1) KVAR = KVA x sqrt(1  pf x pf) = 560 x sqrt(1  0.55 x 0.55)
To calculate the reduction in line current or KVA by the addition of power factor correction for a known initial KVA and power factor and a target power factor, we first calculate the KW from the known KVA and power factor. From that KW and the target power factor, we can calculate the new KVA (or line current). i.e. Initial KVA = 560 Please post a link to this page using the following HTML
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