Amps to kW motor
Convert a motor's running current to the electrical kW it draws and the mechanical kW and horsepower it delivers.
Inputs
Power flow through the motor
How amps to kW motor calculator works
The amps to kW motor calculator converts motor current into electrical input power, shaft output power and horsepower (hp) with 5 inputs: current, voltage, phase, power factor and efficiency. The calculator multiplies input kW by efficiency to get shaft kW.
Pout = √3 × I × V × PF × η / 100015 A at 400 V, PF 0.85 and 90% efficiency gives 8.83 kW input and 7.95 kW (10.66 hp) at the shaft. The flow diagram splits input power into shaft power and heat losses.
Amps to kW motor formula
The amps to kW motor formula is Pout(kW) = √3 × I × V × PF × η / 1,000 for a three-phase motor, where η is efficiency. There are 3 motor formulas: input power, shaft power and horsepower.
Input power
Pin = √3 × I × V × PF / 10001.732 × 15 A × 400 V × 0.85 / 1,000 = 8.83 kW
Shaft power
Pout = Pin × η8.83 kW × 0.9 = 7.95 kW
Horsepower
hp = Pout / 0.74577.95 kW / 0.7457 = 10.66 hp
Motor nameplates list shaft output power under IEC 60034-1 and NEMA MG 1. IEC 60034-30-1 defines 4 efficiency classes, IE1 to IE4, and an IE3 7.5 kW four-pole motor runs at about 90% efficiency.
Amps to kW motor conversion chart
The amps to kW motor conversion chart lists 13 motor ratings from 0.75 kW to 75 kW with horsepower and the full-load amps at 400 V and 480 V three phase, using power factor 0.85 and 90% efficiency.
| Motor | hprating | 400 V 3φamps | 480 V 3φamps | 230 V 1φamps |
|---|---|---|---|---|
| 0.75 kW | 1.01 | 1.42 | 1.18 | 4.26 |
| 1.5 kW | 2.01 | 2.83 | 2.36 | 8.53 |
| 2.2 kW | 2.95 | 4.15 | 3.46 | 12.5 |
| 4 kW | 5.36 | 7.55 | 6.29 | 22.73 |
| 5.5 kW | 7.38 | 10.38 | 8.65 | 31.26 |
| 7.5 kW | 10.06 | 14.15 | 11.79 | 42.63 |
| 11 kW | 14.75 | 20.75 | 17.3 | 62.52 |
| 15 kW | 20.12 | 28.3 | 23.58 | 85.25 |
| 22 kW | 29.5 | 41.51 | 34.59 | 125.04 |
| 30 kW | 40.23 | 56.6 | 47.17 | 170.5 |
| 45 kW | 60.35 | 84.9 | 70.75 | 255.75 |
| 55 kW | 73.76 | 103.77 | 86.48 | 312.59 |
| 75 kW | 100.58 | 141.51 | 117.92 | 426.26 |
A 7.5 kW (10 hp) motor draws 14.15 A at 400 V three phase at PF 0.85 and 90% efficiency.
Amps to kW motor Excel formula
The amps to kW motor Excel formula is =SQRT(3)*A2*B2*C2*D2/1000 with amps in A2, volts in B2, power factor in C2 and efficiency as a decimal in D2.
| A | B | C | D | E | F | |
|---|---|---|---|---|---|---|
| 1 | Amps | Volts | PF | Eff. | Shaft kW | Formula in E |
| 2 | 15 | 400 | 0.85 | 0.9 | 7.95 | =ROUND(SQRT(3)*A2*B2*C2*D2/1000,2) |
| 3 | 28 | 480 | 0.86 | 0.92 | 18.42 | =ROUND(SQRT(3)*A3*B3*C3*D3/1000,2) |
| 4 | 8 | 230 | 0.8 | 0.85 | 1.25 | =ROUND(A4*B4*C4*D4/1000,2) |
Add =E2/0.7457 in column F to convert shaft kW to horsepower.
Amps to kW motor equation
The amps to kW motor equation is Pout = √3 × I × V × PF × η / 1,000, where η is motor efficiency from 0 to 1.
- P
- Shaft output power in kW
- I
- Motor line current in amperes (A)
- V
- Line-to-line voltage (V)
- PF
- Motor power factor at load
- η
- Efficiency, for example 0.9
1 hp equals 0.7457 kW (745.7 W), and 1 kW equals 1.341 hp.
Amps to kW motor FAQ
How many amps does a 7.5 kW motor draw at 400V?
A 7.5 kW motor draws 14.15 A at 400 V three phase, at a power factor of 0.85 and 90% efficiency.
How many kW is a 10 hp motor?
A 10 hp motor is 7.46 kW of shaft output (10 × 0.7457).
Does a motor kW rating show input or output power?
A motor kW rating shows shaft output power. Electrical input power equals output ÷ efficiency: a 7.5 kW motor at 90% efficiency draws 8.33 kW.
What is the power factor of an electric motor?
An electric motor has a power factor of 0.8 to 0.9 at full load and 0.3 to 0.6 at light load. Small single-phase motors sit near 0.7.