Three-Phase Power
Convert between kW, kVA, kVAR, current and power factor for single- and three-phase systems. Enter the voltage and one value (power or current) and get every quantity, plus the recommended kVA to size a UPS or generator with margin. All in your browser.
All quantities
| Quantity | Value | Detail |
|---|
UPS / generator sizing
Rule of thumb: kVA = kW / PF / 0.8. Keep the UPS or
generator running at no more than 80 % to absorb
inrush peaks and future expansion.
How it is calculated · kW, kVA, kVAR and PF
1. Three-phase (V = line-to-line):
kVA = √3 · V · I / 1000 and I = kVA · 1000 / (√3 · V).
Single-phase: without the √3 → kVA = V · I / 1000.
2. The power factor relates apparent to
active power: kW = kVA · PF, where
PF = cosφ is between 0 and 1.
3. The power triangle:
kVA² = kW² + kVAR², so
kVAR = √(kVA² − kW²) (reactive power).
4. Sizing: start from active power and
leave margin → kVA = kW / PF / 0.8. The
0.8 reserves 20 % for inrush and growth.
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