Electric Motors - Torque vs. Power and Speed
- Work is the result of a force acting over some distance. Work is quantified in joules (Nm) or foot-pounds.
- Torque is a rotating force produced by a motor’s crankshaft. The more torque the motor produces, the greater is its ability to perform work. Since torque is a vector acting in a direction it is commonly quantified by the units Nm or pound-feet.
- Power is how rapidly work is accomplished - work in a given amount of time. Power is quantified in watts (J/s) or horse power.
Note that the driving force of an electric motor is torque - not horsepower. The torque is the twisting force that makes the motor running and the torque is active from 0% to 100% operating speed.
The power produced by the motor depends on the speed of the motor and is
- zero at 0% speed, and
- normally at it's top at operating speed
Note ! - the full torque from zero speed is a major advantage for electric vehicles.
For full table - rotate the screen!
Power | Motor Speed (rpm) | |||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
3450 | 2000 | 1750 | 1000 | 500 | ||||||||||||
Torque | ||||||||||||||||
hp | kW | (lbf in) | (lbf ft) | (Nm) | (lbf in) | (lbf ft) | (Nm) | (lbf in) | (lbf ft) | (Nm) | (lbf in) | (lbf ft) | (Nm) | (lbf in) | (lbf ft) | (Nm) |
1 | 0.75 | 18 | 1.5 | 2.1 | 32 | 2.6 | 3.6 | 36 | 3.0 | 4.1 | 63 | 5.3 | 7.1 | 126 | 10.5 | 14.2 |
1.5 | 1.1 | 27 | 2.3 | 3.1 | 47 | 3.9 | 5.3 | 54 | 4.5 | 6.1 | 95 | 7.9 | 10.7 | 189 | 15.8 | 21.4 |
2 | 1.5 | 37 | 3.0 | 4.1 | 63 | 5.3 | 7.1 | 72 | 6.0 | 8.1 | 126 | 10.5 | 14.2 | 252 | 21.0 | 28.5 |
3 | 2.2 | 55 | 4.6 | 6.2 | 95 | 7.9 | 10.7 | 108 | 9.0 | 12 | 189 | 15.8 | 21.4 | 378 | 31.5 | 42.7 |
5 | 3.7 | 91 | 7.6 | 10 | 158 | 13.1 | 18 | 180 | 15 | 20 | 315 | 26.3 | 36 | 630 | 52.5 | 71 |
7.5 | 5.6 | 137 | 11 | 15 | 236 | 20 | 27 | 270 | 23 | 31 | 473 | 39 | 53 | 945 | 79 | 107 |
10 | 7.5 | 183 | 15 | 21 | 315 | 26 | 36 | 360 | 30 | 41 | 630 | 53 | 71 | 1260 | 105 | 142 |
15 | 11 | 274 | 23 | 31 | 473 | 39 | 53 | 540 | 45 | 61 | 945 | 79 | 107 | 1891 | 158 | 214 |
20 | 15 | 365 | 30 | 41 | 630 | 53 | 71 | 720 | 60 | 81 | 1260 | 105 | 142 | 2521 | 210 | 285 |
25 | 19 | 457 | 38 | 52 | 788 | 66 | 89 | 900 | 75 | 102 | 1576 | 131 | 178 | 3151 | 263 | 356 |
30 | 22 | 548 | 46 | 62 | 945 | 79 | 107 | 1080 | 90 | 122 | 1891 | 158 | 214 | 3781 | 315 | 427 |
40 | 30 | 731 | 61 | 83 | 1260 | 105 | 142 | 1441 | 120 | 163 | 2521 | 210 | 285 | 5042 | 420 | 570 |
50 | 37 | 913 | 76 | 103 | 1576 | 131 | 178 | 1801 | 150 | 204 | 3151 | 263 | 356 | 6302 | 525 | 712 |
60 | 45 | 1096 | 91 | 124 | 1891 | 158 | 214 | 2161 | 180 | 244 | 3781 | 315 | 427 | 7563 | 630 | 855 |
70 | 52 | 1279 | 107 | 145 | 2206 | 184 | 249 | 2521 | 210 | 285 | 4412 | 368 | 499 | 8823 | 735 | 997 |
80 | 60 | 1461 | 122 | 165 | 2521 | 210 | 285 | 2881 | 240 | 326 | 5042 | 420 | 570 | 10084 | 840 | 1140 |
90 | 67 | 1644 | 137 | 186 | 2836 | 236 | 321 | 3241 | 270 | 366 | 5672 | 473 | 641 | 11344 | 945 | 1282 |
100 | 75 | 1827 | 152 | 207 | 3151 | 263 | 356 | 3601 | 300 | 407 | 6302 | 525 | 712 | 12605 | 1050 | 1425 |
125 | 93 | 2283 | 190 | 258 | 3939 | 328 | 445 | 4502 | 375 | 509 | 7878 | 657 | 891 | 15756 | 1313 | 1781 |
150 | 112 | 2740 | 228 | 310 | 4727 | 394 | 534 | 5402 | 450 | 611 | 9454 | 788 | 1069 | 18907 | 1576 | 2137 |
175 | 131 | 3197 | 266 | 361 | 5515 | 460 | 623 | 6302 | 525 | 712 | 11029 | 919 | 1247 | 22058 | 1838 | 2494 |
200 | 149 | 3654 | 304 | 413 | 6302 | 525 | 712 | 7203 | 600 | 814 | 12605 | 1050 | 1425 | 25210 | 2101 | 2850 |
225 | 168 | 4110 | 343 | 465 | 7090 | 591 | 801 | 8103 | 675 | 916 | 14180 | 1182 | 1603 | 28361 | 2363 | 3206 |
250 | 187 | 4567 | 381 | 516 | 7878 | 657 | 891 | 9003 | 750 | 1018 | 15756 | 1313 | 1781 | 31512 | 2626 | 3562 |
275 | 205 | 5024 | 419 | 568 | 8666 | 722 | 980 | 9904 | 825 | 1120 | 17332 | 1444 | 1959 | 34663 | 2889 | 3918 |
300 | 224 | 5480 | 457 | 620 | 9454 | 788 | 1069 | 10804 | 900 | 1221 | 18907 | 1576 | 2137 | 37814 | 3151 | 4275 |
350 | 261 | 6394 | 533 | 723 | 11029 | 919 | 1247 | 12605 | 1050 | 1425 | 22058 | 1838 | 2494 | 44117 | 3676 | 4987 |
400 | 298 | 7307 | 609 | 826 | 12605 | 1050 | 1425 | 14405 | 1200 | 1628 | 25210 | 2101 | 2850 | 50419 | 4202 | 5699 |
450 | 336 | 8221 | 685 | 929 | 14180 | 1182 | 1603 | 16206 | 1351 | 1832 | 28361 | 2363 | 3206 | 56722 | 4727 | 6412 |
550 | 410 | 10047 | 837 | 1136 | 17332 | 1444 | 1959 | 19808 | 1651 | 2239 | 34663 | 2889 | 3918 | 69326 | 5777 | 7837 |
600 | 448 | 10961 | 913 | 1239 | 18907 | 1576 | 2137 | 21608 | 1801 | 2443 | 37814 | 3151 | 4275 | 75629 | 6302 | 8549 |
Electrical Motor Power, Velocity and Torque Equations
Torque in Imperial units can be calculated as
Tinlb = Php 63025 / n (1)
where
Tinlb = torque (in lbf )
Php = horsepower delivered by the electric motor (hp)
n = revolution per minute (rpm)
Alternatively
Tftlb = P hp 5252 / n (1b)
where
Tftlb = torque (lbf ft)
- 1 ft lbf = 1.356 Nm
Torque in SI units can be calculated as
TNm = PW 9.549 / n (2)
where
TNm = torque (Nm)
PW = power (watts)
n = revolution per minute (rpm)
Electric Motor - Torque vs. Power and Speed
- 1 hp = 0.746 kW - power converter
- 1 lb ft = 1.355 Nm - torque converter
Electric Motor - Power vs. Torque and Speed
Electric Motor - Speed vs. Power and Torque
Example - Torque from an Electrical Motor
The torque delivered from an electrical motor producing 0.75 kW (750 W) at speed 2000 rpm can be calculated as
T = ( 750 W ) 9.549 / (2000 rpm)
= 3.6 (Nm)
Example - Torque from an Electrical Motor
The torque delivered from an electrical motor producing 100 hp at speed 1000 rpm can be calculated as
T = (100 hp) 63025 / (1000 rpm)
= 6303 < (lbf in)
To convert to pound-force foot - divide the torque by 12 .
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