Power Factor Correction Capacitor Calculator
Size a power factor correction capacitor bank. The workbook calculates the kVAR needed to reach your target power factor, the drop in current and kVA, and the capacitance per phase for star or delta connection.
Download
- Calculator sheet with a worked example
- How to Use sheet with steps
- 31 built in formulas, no macros
- Yellow input cells, grey results
- Calculation sign off block
- Excel, Google Sheets and LibreOffice
Worked Example
These are the results of the example already filled in the workbook. Replace the yellow cells with your own data.
kVAR for other target power factors
| Target PF | kVAR needed | Line current (A) | kVA |
|---|---|---|---|
| 0.85 | 13.0 | 163.7 | 117.6 |
| 0.90 | 26.6 | 154.6 | 111.1 |
| 0.92 | 32.4 | 151.2 | 108.7 |
| 0.95 | 42.1 | 146.4 | 105.3 |
| 0.97 | 49.9 | 143.4 | 103.1 |
| 0.98 | 54.7 | 142.0 | 102.0 |
| 0.99 | 60.8 | 140.5 | 101.0 |
| 1.00 | 75.0 | 139.1 | 100.0 |
About this Calculator
Low power factor raises current, cable losses and the demand charge on the electricity bill. Capacitor banks are a simple fix when sized correctly; this workbook shows how much correction you need and what it saves in current and kVA.
Basis: Power triangle: Qc = P × (tan φ1 − tan φ2); capacitance from Q = V² × 2πfC.
How to use
- Enter the load power in kW, the existing and target power factor, voltage and frequency.
- Choose star or delta for the capacitor bank.
- Read the kVAR rating, current reduction and capacitance per phase.
- Use the table to compare the cost of different target power factors.
Formulas used
- Qc = P × (tan(acos PF1) − tan(acos PF2)).
- I = P ÷ (√3 × V × PF).
- Delta: C per phase = Qc ÷ 3 ÷ (2πf V²); Star: C per phase = Qc ÷ (2πf V²).
Related tools
Frequently Asked Questions
How do I calculate kVAR for power factor correction?
kVAR = kW × (tan φ1 − tan φ2), where φ1 and φ2 are the angles of the existing and target power factor.
What target power factor should I choose?
Usually 0.95 to 0.98. Going to unity costs more and risks leading power factor at light load.
Why does capacitance differ for star and delta?
In delta each capacitor sees line voltage; in star it sees phase voltage, so star needs three times the capacitance for the same kVAR.
Learn more on the blog
Basics of Ohm's law
A practical guide on instrumentationblog.in that explains the engineering behind this workbook.
Read Full Article