What is the smallest electric motor capable of lifting 250 pounds?
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.
