Result
Preliminary calculation: This tool is for quick sizing and information. In real projects, load calculation, selection and commissioning require engineering calculations and a site survey. Results are approximate values.
Formulas
Three phase: P [kW] = √3 × V × I × cosφ / 1000Single phase: P [kW] = V × I × cosφ / 1000For motor loads (compressor, pump, fan), the power factor is usually less than 1. Current and voltage values on the nameplate give more accurate results. Since starting current can be several times the rated current, fuse and contactor selection is evaluated separately.
- Nameplate values (kW, A, V, cosφ) are the most reliable source
- Phase sequence and phase imbalance affect motor life
- Insufficient cable cross-section causes voltage drop and overheating
Frequently asked questions
How do you find amps from kW in 3 phase?
Divide the power (W) by the product of √3, voltage and cosφ.
What is cosφ?
It is the power factor; it gives the ratio of real power to apparent power. For motor loads it is typically around 0.8–0.9.
Can I select a cable with this value?
No. Cable cross-section requires a separate calculation that includes factors such as current-carrying capacity, installation method and voltage drop.