Commonly method for power factor correction using the capacitor to generate reactive power ( kVAR ) to reduce apparent power ( kVA ) form inductive load.
This time i want share a simple method to sizing our capacitor to improve power factor for induction motor and utility electricity.This method also can use for capacitor bank sizing.
How to sizing capacitor for power factor correction?
To properly sizing the amount of capacitor (kVAR) required to correct the lagging power factor,we must have three (3) important of information below:
- kW (kilowatts)
- Existing Power Factor ( % )
- Desired Power Factor ( % )
From this information,now we can calculate the capacitor size for power factor correction.The formula to calculate the required kVAR is:
Factor from Table 1 below x kW = kVAR of capacitors required.
Calculation Example :
1 unit air-compressor ( 3 phase 415 VAC ) used an average of 90 kW with an existing power factor of 80%.The desired power factor is 95%. The factor value for this case is 0.421 to raise the power factor from 80% to 95% using table 1.
0.421 x 90 kW = 38 kVAR
So we need capacitor size 38 kVAR to get power factor 95% for 1 unit air-compressor 90 kW.
If working power (kW) or Present Power Factor are not known you can calculate from the following formulas to get the three basic pieces of information required to calculate kVAR.The best range for desired power factor is around 95% until 100%.