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16 January 2006
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DOMESTIC PRODUCT |
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How does it work?
Power Factor is a ratio between the KW and the KVA drawn by an electrical load where the KW is the actual 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.
All current will causes loses in the supply and distribution system. A load with a power factor of 1.0 results in the most efficient loading of the supply and a load with a power factor of 0.5 will result in much higher loses in the supply system.
A poor power factor can be result of either a significant phase difference between the voltage and current at the load terminals, or it can be due to a high harmonic content or distorted/discontinuous current waveform.
A poor load current phase angle is generally the result of an inductive load such as an induction motor, power transformer, lighting ballasts, welder, or induction furnace.
A power factor due to an inductive load can be improved by addition of power factor correction. Many inverters are quoted as having a power factor of better than 0.95 when in reality, the true power factor is between 0.5 and 0.75. The figure of 0.95 is based on the Cosine of the angle between the voltage and current but does not take into account that the current waveform is discontinuous and therefore contribute to increased losses on the supply.
BEFORE AND AFTER ‘ ENERGY SAVER ’ (ES)
Q1 = Apparent power before GES
Q2 = Apparent power after GES
W1 = Reactive power before GES installation
W2 = Reactive power after GES installation
Wd = W1 – W2 (different in reactive power usage
Ø1 = Phase angle shifted before ES
Ø2 = Phase angle shifted after ES
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POWER FACTOR CORRECTED ON AC LINE CURRENT WAVEFORM


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