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# Electric Motors - Torque vs. Power and Speed

## Electric motor output power and torque vs. rotation 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!

PowerMotor Speed (rpm)
3450200017501000500
Torque
hpkW(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 = Php 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)

power (kW)

speed (rpm)

torque (Nm)

speed (rpm)

power (kW)

torque (Nm)

### 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 W9.549 / (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.

## Related Topics

• Electrical - Electrical units, amps and electrical wiring, wire gauge and AWG, electrical formulas and motors.

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## Citation

• Engineering ToolBox, (2009). Electric Motors - Torque vs. Power and Speed. [online] Available at: https://www.engineeringtoolbox.com/electrical-motors-hp-torque-rpm-d_1503.html [Accessed Day Mo. Year].

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