kW, kVA, HP and Amps Converter

The difference between kW and kVA

kW is active power and kVA is apparent power. The ratio between them is the power factor: kVA = kW / cos φ. A 75 kW load at a power factor of 0.8 draws 93.75 kVA. Generators and transformers are sized in kVA, while energy use is counted in kW. The calculator also gives reactive power in kvar.

How many kW is one horsepower?

There are two different horsepower units and they are often mixed up.

• Mechanical horsepower (hp): 745.7 W. Used for motors and pumps of British and US origin.
• Metric horsepower (PS, CV): 735.5 W. Used in European catalogues and for vehicles.

10 hp equals 7.457 kW or 10.14 PS. Whichever unit you enter, the calculator shows all three.

How many amps is a kW?

Current depends on voltage, the number of phases and the power factor.

• Single phase: I = P / (V × cos φ × η)
• Three phase: I = P / (√3 × V × cos φ × η)

A motor nameplate shows shaft power, which is why efficiency (η) is also in the denominator. A three phase 400 V, 15 kW motor with a power factor of 0.85 and 90 percent efficiency has a rated current of 15000 / (1.732 × 400 × 0.85 × 0.9) = 28.3 A.

Going from kVA to amps needs no power factor: a 400 V, 100 kVA transformer has a rated current of 100000 / (1.732 × 400) = 144.3 A.

Limits

The result is the continuous current at rated load. Starting current, unbalanced loads and harmonics are not included. Cable and protective device selection starts from this current but must be done separately under the applicable standard.