As the question implies, How much current does a 24v 750w dc Motor uses

I have tried i=p/v = 750/24 = 31.25A

Which the result seems unreal to me as only 0.1A is capable to kill a human

Thankyou in advance, C. Shockley

  • 10
    \$\begingroup\$ Generally you run that current through a cable to the motor, not through a human... \$\endgroup\$
    – PlasmaHH
    Feb 22 '16 at 16:43
  • \$\begingroup\$ That seems reasonable. Car starter motors may use 100A in short bursts. \$\endgroup\$
    – pjc50
    Feb 22 '16 at 16:47
  • \$\begingroup\$ The DC motor looks like a resistance of about 1ohm to the voltage source. You would present a much higher resistance, therefore a much lower current would pass through your body. \$\endgroup\$
    – Chu
    Feb 22 '16 at 17:19

This should be correct, but take note that on startup it uses a lot higher current than that (until it spins in full speed).


Your equation is for the nominal operating point. If you want to have (750W - losses) mechanical output you need 750W as electrical input. It should be approximately right and the value is totally real.

The human analogy is not a good comparison here, because we are not a good power electric device like a motor, we are constructed for small signal electronics: transmitting control signals from the brain to the muscles.

  • \$\begingroup\$ I agree with your answer, it is very well put. But to my experience (or at least, in my country) when motor power is specified in Watts, it is already referring to the electric "input" power. Mechanical power output would be specified in a different unit, like horsepower. Therefore, such specifications would make me consider losses already being accounted for, with a mechanical output lower than 750 W. IMO this is a big source for ambiguity. \$\endgroup\$ Feb 22 '16 at 19:15
  • \$\begingroup\$ Yes I think you are right. As far as I know I should have written it that way. I edited my answer. \$\endgroup\$
    – c-a
    Feb 22 '16 at 19:20

Electrical input power of the motor on the name plate is actually for the full rated mechanical power output of the motor.

Thus a 750W motor run from 24 V will not demand 30Amp without mechanically coupled to anything significant.

There is no law to say mechanical power must only be stated in horsepowers. One horsepower is 746W and this means the motor is one HP motor.

This motor during free run (zero mechanical load) probably will demand a mere 5 Amps or even less.


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