Power and current converter

On single- and three-phase networks, convert between power and current with a power factor; the result also gives the apparent power.

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Which formulas does the converter use?

• Single-phase network (230 V): I = P / (230 · cos φ), that is P = I · 230 · cos φ.
• Three-phase network (400 V): I = P / (√3 · 400 · cos φ), that is P = √3 · 400 · I · cos φ.

P is the active power in watts and cos φ is the power factor. The result also gives the apparent power (VA): this is the active power divided by the power factor.

What should the power factor be?

For a resistive load, such as a heater, an electric boiler or an incandescent lamp, it can be taken as 1. For motors, compressor appliances and many electronic loads it is lower; use the value on the rating plate. If you do not know it, 1 gives a smaller current than the real one, so the error is not on the safe side.

What to use it for

For a quick check: how many amps an 11 kW three-phase load draws, how much power a 16 A single-phase circuit can carry. To select the cable and the MCB, use the cable cross-section and MCB calculator.

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