Power Factor Correction Using Capacitor
To determine the value of KVA we use the right angle rule. It is square root of the sum of KW and KVAR.
KVA= Sqrt (KW2 + KVAR2)
To increase the power factor, we need to reduce the amount of required KVA. To do so, we have to shorten the line of KVAR, and this work is done by introducing a capacitor. The capacitor subtracts the extra KVAR and improves the power factor.
These capacitors are available on the market based on how much KVAR value you need to reduce to get the desired power factor.
Let we take a look how the calculation of the correction is done.
First of all we need to measure the amount of apparent power or KVA required for the transformer to work. After getting this value, you need to determine what the power factor of the transformer is and how much power factor you want to get.
Suppose, your transformer requires 560 KVA to operate and it has the power factor 0.55. You want to increase this power factor to 0.95.
You need to use the formula given below to determine the value of KVAR.
KVAR = KVA*(1-pf2)
Now, follow the three steps given below to determine how much KVAR value you need to reduce.
- Calculate the value of KVAR using value of the present power factor.
KVAR1 = 560*(1-0.552)
KVAR1 = 467.
- Calculate the value of KVAR using desired value of power factor.
KVAR2 = 560*(1-0.952)
KVAR2 = 175
Now, subtract KVAR1 by KVAR2. You will get 292 KVAR.
You can use this value to purchase the exact capacitor so as you would get the desired value of power factor.
You can also use the power factor table to determine the required reduction in KVAR. Follow the steps given below to use this table.
- Determine the original power factor of the transformer and also the desired power factor.
- Get the value in the table where the row of original power factor and column of desired power factor meet.
- Determine the value of KW. If you have KVA value, divide the KVA by the original power factor to get KW.
- Now multiply KW with the value you have gotten in the table. This is the KVAR that is required to reduce.