What is horsepower?

Horsepower is a measure of the work done by an AC motor. 1 HP can be visualized by the image of a horse, or a 1 HP motor, lifting a 550 lbs by 1 foot over 1 second. More weight means a slower lift.



HP on the Nameplate



Horsepower and RPM

The horsepower listed on the motor’s nameplate is achieved at the Nameplate RPM. Horsepower and RPM share a linear relationship. For example, an 1800 RPM motor operating at half speed will produce half the horsepower.



Torque

Torque is the driving rotational force of an AC motor. Torque is what produces horsepower, or the motor’s ability to do work at a given rate. HP is understood as a product of the motor’s torque and RPM.



HP vs kW

The work performed by an AC motor is measured in two different ways: Horsepower (HP) and Kilowatts (kW). Both are units of power and are preferred in different parts of the world. 1Hp equals 0.746 kW (while 1 kW equals 1.34 HP).



Other Considerations

Voltage

Your chosen motor’s voltage should match the supply voltage available to you. Motors typically have more than one possible voltage depending on how they are wired.


Revolutions Per Minute (RPM)

RPM represents the speed of the motor. The rated RPM is specific to the frequency stated on the motor’s nameplate, and a different frequency will produce different results..


Frame

The size of the actual frame of a given frame size may vary slightly between manufacturers, but a frame size notation is a universal reference to shaft diameter, shaft length, and mounting footprint. Given motors from two different manufacturers with the same state frame size, those three dimensions will remain consistent.