75kW 3000rpm motor torque — 239 N·m
A 75kW 3000rpm motor delivers 239 N·m of rated torque. That is 75000 W divided by an angular velocity of 314.16 rad/s, the same torque written as 24.3 kgf·m or 176 lb·ft. In horsepower, 75 kW is 102 PS on the metric definition and 101 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.
- 50 Hz · 3000 rpm239 N·m
- 60 Hz · 3600 rpm199 N·m
- Rated output
- 75 kW · 75000 W
- Synchronous speed
- 3000 rpm
- Mains frequency
- 50 Hz
- Poles
- 2
- Angular velocity
- 314.16 rad/s
- Torque
- 239 N·m
- Torque in kgf·m
- 24.3 kgf·m
- Torque in lb·ft
- 176 lb·ft
- Metric horsepower (PS)
- 102 PS
- Mechanical horsepower (hp)
- 101 hp
- Full-load speed
- 2910 rpm · 246 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 · 1000 rpm680 N·m
- Gear ratio 5 · 600 rpm1130 N·m
- Gear ratio 10 · 300 rpm2270 N·m
- Gear ratio 20 · 150 rpm4540 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.
- 230 V · cosφ 0.87 · η 0.92235 A
- 400 V · cosφ 0.87 · η 0.92135 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 75kW 3000rpm motor make?
239 N·m — 75000 W divided by an angular velocity of 314.16 rad/s. The same figure is 24.3 kgf·m or 176 lb·ft.
Q. What happens through a 10:1 gearbox?
The speed drops to 300 rpm and the torque rises to 2270 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 50 Hz: 235 A at 230 V, 135 A at 400 V. This assumes a representative power factor of 0.87 and efficiency of 0.92, so use the nameplate figures when you have them.