Alternating Current
Power Factor Correction Calculator
Power Factor Correction helps you find required capacitor reactive power from real power, initial power factor, target power factor, frequency, and line voltage. The page keeps the arithmetic visible so you can check the result against the original measurements.
Calculate Required capacitor reactive power
Enter ratings or measurements that describe one scenario.
Understanding the equation
This page evaluates Qc = P(tan φ₁ − tan φ₂); C depends on line voltage and connection. The formula draws on Real power, Initial power factor, Target power factor, Frequency, and Line voltage.
With the current entries, the primary answer is 12,703 var. Preserve the raw inputs when replacing this example.
Size a three-phase correction bank from power, power factors, frequency, and voltage. A connected part of the work can be checked with Line Phase Voltage Calculator.
Sensitivity check
Change Real power from 20 kW to 24 kW with the rest of the inputs held constant. The comparison runs from 12,703 var to 15,244 var.
Do not average the two cases if either could define an operating limit.
Values this page needs
Keep distorted-waveform measurements separate from sine-wave assumptions. A source note beside each entry makes the result reproducible.
A denominator entry cannot be zero. Convert units once, retain the original reading, and verify the converted magnitude.
- Real power
- Default example: 20 kW. Enter real power in kW.
- Initial power factor
- Default example: 0.72. Enter initial power factor.
- Target power factor
- Default example: 0.95. Enter target power factor.
- Frequency
- Default example: 50 Hz. Enter frequency in Hz.
- Line voltage
- Default example: 400 V. Enter line voltage in V.
Checks that catch bad inputs
An unlabeled assumption can make an otherwise correct result unusable.
Compare the magnitude with a quick independent estimate.
How to use the result
The primary answer, Required capacitor reactive power, describes only the entered scenario. Compare it with impedance, phase, waveform, and equipment ratings.
Store the measurement state and conversion notes with the answer.
Practical limits
Check harmonics, switching steps, and resonance before selecting capacitors.
The arithmetic intentionally leaves out harmonics, phase imbalance, saturation, and nonsinusoidal current. Do not hide omitted behavior inside an unexplained correction factor.
Keep distorted-waveform measurements separate from sine-wave assumptions.
Before relying on the answer
Why does the field result disagree with this page?
Differences can come from startup transients, resonance, and measurement bandwidth, measurement uncertainty, or values taken under different conditions.
How should I compare two Power Factor Correction cases?
Use separate labeled cases when more than one condition changes. Use RMS values unless an input explicitly requests peak amplitude.
What else is required before final selection?
The calculator does not approve equipment or supply an unexplained margin. Compare against impedance, phase, waveform, and equipment ratings.
Should intermediate values be rounded?
Do not round between dependent calculations. Match the final display to the precision of the source data.
Which entries must stay above zero?
A zero denominator is undefined, so the affected field has a positive minimum.
How should I prepare the Power Factor Correction inputs?
Use real power, initial power factor, target power factor, frequency, and line voltage from one operating condition. Use RMS values unless an input explicitly requests peak amplitude.