Three-phase current equation
For balanced three-phase systems, current can be calculated from either real power in kW or apparent power in kVA.
I = P × 1000 / (√3 × VL-L × PF × η)I = S × 1000 / (√3 × VL-L)where:
- I
- Balanced three-phase line currentA
- P
- Real powerkW
- S
- Apparent powerkVA
- VL-L
- Line-to-line voltageV
- PF
- Power factor
- η
- Efficiency as a decimal
The equation assumes a balanced load. Motor starting current, harmonics, and unbalanced phase loading require separate checks.
Assumptions
- Balanced three-phase load
- Line-to-line voltage input
Important Warnings
- Starting current and harmonics are not included.
- Use actual equipment nameplate data for final selection.
FAQ
Should I enter phase voltage or line voltage?
Enter line-to-line voltage, such as 400 V, 480 V, or 690 V.
Why is power factor ignored for kVA?
kVA is apparent power, so current can be calculated directly from apparent power and voltage.