100 kVA at power factor 0.8 = 80 kW. A 33.7 kVAr capacitor bank would lift the power factor to 0.95, cutting current from 144 A to 122 A (−29% cable losses) and freeing 15.8 kVA of capacity.
Real power
80kW
power factor 0.8
Apparent power
100kVA
Reactive power
60kVAr
Line current (per phase)
144.3A
I = S ÷ (√3 × 400 V)
Phase angle φ
36.9°
Power in horsepower
107.3hp
Capacitor bank for PF 0.95
33.7kVAr
Current after correction
121.5A
−16% current
kVA after correction
84.21kVA
Same apparent power at other power factors
| Power factor | kW | kVAr | Current (A) |
|---|---|---|---|
| 1 | 100 | 0 | 144.3 |
| 0.95 | 95 | 31.22 | 144.3 |
| 0.9 | 90 | 43.59 | 144.3 |
| 0.85 | 85 | 52.68 | 144.3 |
| 0.8 | 80 | 60 | 144.3 |
| 0.75 | 75 | 66.14 | 144.3 |
| 0.7 | 70 | 71.41 | 144.3 |
Standard generator / transformer sizes at PF 0.8
| kVA | kW | Amps @ 400 V 3-ph |
|---|---|---|
| 10 | 8 | 14 |
| 20 | 16 | 29 |
| 30 | 24 | 43 |
| 50 | 40 | 72 |
| 63 | 50 | 91 |
| 100 | 80 | 144 |
| 160 | 128 | 231 |
| 250 | 200 | 361 |
| 400 | 320 | 577 |
| 630 | 504 | 909 |
| 1,000 | 800 | 1,443 |
| 1,600 | 1,280 | 2,309 |
| 2,500 | 2,000 | 3,608 |
- kVA is what cables, transformers and generators must carry; kW is the power that does useful work. The ratio is the power factor.
- Generators are usually rated in kVA at 0.8 PF, so a 100 kVA genset delivers at most 80 kW of real power.
- Capacitor sizing assumes a sinusoidal supply. With many drives or inverters (harmonics), use detuned capacitor banks or active filters and have an engineer check for resonance.