Method
Reactive-power and apparent-power change from existing to target power factor.
Equations
φ1 = arccos(PF1)
φ2 = arccos(PF2)
Q1 = P · tan φ1
Q2 = P · tan φ2
Qc = Q1 − Q2
S1 = PPF1
S2 = PPF2
Symbols and units
| Symbol | Quantity | Unit |
|---|---|---|
| Inputs | ||
| P | Active power | kW |
| PF1 | Existing power factor | 0–1 |
| PF2 | Target power factor | 0–1 |
| Intermediate values | ||
| φ1 | Existing phase angle | – |
| φ2 | Target phase angle | – |
| Results | ||
| Q1 | Existing reactive power | kvar |
| Q2 | Target reactive power | kvar |
| Qc | Required capacitor | kvar |
| S1 | Existing apparent power | kVA |
| S2 | Target apparent power | kVA |
Assumptions and limits
- No commercial capacitor-step size is selected.
In practice
- Choose the capacitor bank and its steps from the maker’s standard ratings at or above Qc.
Worked example
The input values are the calculator's own verification test, run through the calculator. They show the working; they are not design values.
Inputs
| P | Active power | 100 kW |
| PF1 | Existing power factor | 0.75 0–1 |
| PF2 | Target power factor | 0.93 0–1 |
Results
| Q1 | Existing reactive power | 88.1917 kvar |
| Q2 | Target reactive power | 39.5225 kvar |
| Qc | Required capacitor | 48.6692 kvar |
| S1 | Existing apparent power | 133.333 kVA |
| S2 | Target apparent power | 107.527 kVA |
A preliminary check for engineer review, not an engineering approval. The project calculation to the applicable codes, authority requirements and specification governs.