15kW 3600rpm motor torque — 39.8 N·m
A 15kW 3600rpm motor delivers 39.8 N·m of rated torque. That is 15000 W divided by an angular velocity of 376.99 rad/s, the same torque written as 4.06 kgf·m or 29.3 lb·ft. In horsepower, 15 kW is 20.4 PS on the metric definition and 20.1 hp on the mechanical one.
Poles and mains frequency fix the speed
The synchronous speed of an induction motor is not a choice: it is 120 × frequency ÷ poles. The same four-pole motor therefore turns at 1800 rpm on 60 Hz and 1500 rpm on 50 Hz — Korea, the United States and eastern Japan run 60 Hz, while Europe, China and India run 50 Hz. Same power, speeds in a 6 : 5 ratio, so the torques land in a 5 : 6 ratio. In service the rotor lags by the slip, which is why the nameplate reads something like 1746 rpm.
- 60 Hz · 3600 rpm39.8 N·m
- 50 Hz · 3000 rpm47.7 N·m
- Rated output
- 15 kW · 15000 W
- Synchronous speed
- 3600 rpm
- Mains frequency
- 60 Hz
- Poles
- 2
- Angular velocity
- 376.99 rad/s
- Torque
- 39.8 N·m
- Torque in kgf·m
- 4.06 kgf·m
- Torque in lb·ft
- 29.3 lb·ft
- Metric horsepower (PS)
- 20.4 PS
- Mechanical horsepower (hp)
- 20.1 hp
- Full-load speed
- 3492 rpm · 41 N·m
Through a gearbox
Put a reduction ratio i in the path and the output shaft turns at 1/i of the speed while the torque grows i-fold. Power does not grow — it shrinks by the efficiency η, so the torque is i × η times the input. The figures here assume η = 0.95, typical of a helical gearbox. A worm drive falls to 0.5–0.8 and delivers far less. More torque never means more energy: the same power is simply traded for slower, heavier turning.
- Gear ratio 3 · 1200 rpm113 N·m
- Gear ratio 5 · 720 rpm189 N·m
- Gear ratio 10 · 360 rpm378 N·m
- Gear ratio 20 · 180 rpm756 N·m
Three-phase current by voltage
For a three-phase induction motor the current is I = P ÷ (√3 × V × cosφ × η). Rated output is what leaves the shaft, so the electrical input is larger by the efficiency, and only the working share of that counts through the power factor. Supply voltage differs by country, so the same motor draws 1.7 times as much at 220 V as at 380 V. The power factor and efficiency used here are representative values by frame size; the nameplate carries the real ones and should be read first.
- 220 V · cosφ 0.87 · η 0.9249.2 A
- 380 V · cosφ 0.87 · η 0.9228.5 A
- 460 V · cosφ 0.87 · η 0.9223.5 A
Nearby cells
Same output, other speeds
Same speed, other outputs
Worth knowing
- Torque (N·m) is power (W) divided by angular velocity (rad/s), and that velocity is 2π × rpm ÷ 60.
- The 9550 in T = 9550 × P(kW) ÷ n(rpm) is 60000 ÷ 2π rounded up.
- At constant power, doubling the speed halves the torque — they are inversely proportional.
- Metric horsepower (PS) is 735.49875 W and mechanical horsepower (hp) is 745.699872 W: different numbers.
Related tables
Common questions
Q. How much torque does a 15kW 3600rpm motor make?
39.8 N·m — 15000 W divided by an angular velocity of 376.99 rad/s. The same figure is 4.06 kgf·m or 29.3 lb·ft.
Q. What happens through a 10:1 gearbox?
The speed drops to 360 rpm and the torque rises to 378 N·m. It is not a clean 10-fold gain because the gearbox efficiency of 0.95 is applied as well.
Q. How much three-phase current does it draw?
On 60 Hz: 49.2 A at 220 V, 28.5 A at 380 V, 23.5 A at 460 V. This assumes a representative power factor of 0.87 and efficiency of 0.92, so use the nameplate figures when you have them.