What equation is used to determine the horsepower of a motor?

The equation used to determine the horsepower of a motor when considering fluid movement, such as in pumps, is crucial for understanding how efficiently a motor can move a certain volume of liquid over a specified distance. The correct formula involves the flow rate, measured in gallons per minute (gpm), multiplied by the head in feet (the height the fluid needs to be lifted), and then further adjusted by the factor of 3960 and the pump's efficiency.

The factor of 3960 is derived from converting the work done (in foot-pounds) to horsepower. It reflects the conversion of energy units and is essential in calculating how much power is truly needed to operate the motor efficiently given the specific application. The efficiency factor accounts for real-world conditions, as no pumping system is 100% efficient; thus, the formula adjusts the theoretical horsepower based on how efficiently the pump operates.

Therefore, the equation not only calculates the power required considering the physical aspects of the fluid movement but also incorporates the real efficiency of the system, which is a critical component in ensuring proper motor selection and system performance.