Single & three phase formulas
| Quantity | Single phase | Three phase (line values) |
|---|---|---|
| Apparent power (VA) | V × I | √3 × VL × IL |
| Real power (W) | V × I × pf | √3 × VL × IL × pf |
| kVA | (V × I) ÷ 1000 | (√3 × VL × IL) ÷ 1000 |
| Current from power | P ÷ (V × pf) | P ÷ (√3 × VL × pf) |
Motor current from horsepower: I = (HP × 746) ÷ (V × eff × pf), and for three phase divide again by √3 → I = (HP × 746) ÷ (√3 × VL × eff × pf). One horsepower is 746 watts; efficiency and power factor are fractions between 0 and 1.
These are physics relationships, safe to state. The nameplate full-load current of a specific motor, and any code full-load-current value, come from the nameplate and your code book — not from here.
√3 ≈ 1.732. pf = power factor. eff = efficiency.
Power factor and the wye/delta line-versus-phase distinction are explained in the glossary.
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