3 steps to simplify your capacitor bank sizing calculations
Once the basics of reactive power compensation, capacitors and their functions and the need for detuned reactors is understood, the next step is choosing capacitor bank sizing, number of steps and other details of the power factor correction capacitor bank.
Here are 3 steps that take you through the process of selecting the right power factor correction unit based on the network characteristics.
3 steps to simplify your capacitor bank sizing calculations
The single line diagram above can be used as a test case to explain the process.
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Identify all Key Network Parameters
The first step is to identify all the key network parameters required to compute the required kVAr of the Power Factor Correction Unit. Primarily, these are the Network Voltage and Frequency, and the Apparent and Actual Power of the installation.- Network Voltage U = 415 V
- Network Frequency f = 50 Hz
- Apparent Power of the Installation P (kVA) = 1500 kVA
- Actual Power of the installation P (kW) = 1182.5 kW
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Determine the Uncompensated Power Factor and Targeted Power Factor for the Network
The second step is to identify the present uncompensated Power Factor of the network. Next, consider Utility requirements and type of installation to set the Target Power Factor level of the network.- Uncompensated Power Factor cos Φ of the network = 0.80
- Targeted Power Factor cos Φ’ of the network = 0.92
(may differ based on installation and utility requirement)
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Perform Calculations to determine Capacitor Bank size (kVAr)
The final step is to calculate the proposed Capacitor bank rating. This is done as detailed below.- Equivalent Uncompensated tan Φ of the network = 0.75
- Equivalent Targeted tan Φ’ of the network = 0.43
- Now, subtract the two values (tan Φ – tan Φ’) = 0.32
- Capacitor Bank required to achieve Targeted Power
- Factor Qc = P kW * (tan Φ – tan Φ’) = 378.3
Hence, a Capacitor Bank of 400 kVAr is required to achieve our target Power Factor in this case.
The steps detailed here can be used for any installation to determine the right size of Power Factor Correction units required.
Download our Handbook on Power Factor Correction
