13-03-2012, 03:42 PM
Power Factor and improvement
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Capacitance
Xc=106/2 fC = V/I
Capacitor current = kVAr x 1000 / V
The opposition to current in a capacitor is termed as capacitive reactance. The current in a purely capacitive circuit will lead the voltage by 90.
Effect of low power factor
kW capacity of the transformer is decreased
Cross-sectional area of the busbars and the switchgear must be increased
The kVA capacity of the alternator is more
Example
Let us suppose that the existing underground cable feeding the workshop is rated for 125 A maximum, at 0.8 power factor. If the power factor is, say, 0.7, then the cable will be overloaded with a current of 143 A.
Improved power factor
Advantages
This increases the kW capacity of the alternators.
The kW capacity of transformers and the lines are increased.
The efficiency of every plant is increased.
The overall cost per unit decreases.
The regulation of the lines is improved.
