what is the smallest electric motor capable of lifting 250 pounds?

Question

Max Volts 12 Volts D.C.
Should move 250 Lb's at a speed of 5 feet per second.

Answer 1

1hp = 550 ft*lb
5*250/550 = 2.27 hp ==> 2.5 hp minimum

Answer 2

Power = work / time = (force x distance) / time.

Power = (250 lbf x 5 feet) / 1 second = 1250 ft-lbf/sec

In the US, a motor is rated in horsepower, a unit developed by James Watt back in the 1700’s as a way to rate the output of steam engines. We could go into a long explanation of how the unit was derived, but a simple search of Wikipedia will provide the details.

In the US, motors are rated in horsepower where 1 HP = 33,000 ft-lbf/min

Convert the earlier answer from seconds to minutes by multiplying by 60.

1250 ft-lbf/sec x 60 sec / min = 75,000 ft-lbf/min.

75,000 ft-lbf/min x 1 HP / 33,000 ft-lbt/min = 2.27 HP

Since you cannot purchase a 2.27 HP motor, we’ll round this up to 2½ HP.



The question includes a motor voltage of 12 V dc. Let’s figure out the current requirements of the motor. First we’ll convert to SI units with the conversion factor 1 HP = 746 watts.

2.27 HP x 746 watts / HP = 1693 watts.

For a dc motor, watts = volts x amps.
Amps = 1693 watts / 12 volts = 141 amps.

Answer 3

1/2 horsepower motor can lift 250 pounds one foot in less than one second.