Which load type is classified as constant horsepower loads?

• A. Fans, centrifugal blowers, and centrifugal pumps
• B. Hoists, conveyors, mixers, and reciprocating or rotary compressors
• C. Wheel grinders, large driller machines, lathes, planers, and boring machines
• D. All of the above

Answer: (C)

Constant horsepower loads are ones where the motor’s power is kept essentially the same across a range of speeds. Since Power equals Torque times Speed, maintaining roughly constant power means the torque must decrease as speed increases. Machine tools such as wheel grinders, large drillers, lathes, planers, and boring machines fit this pattern because they are designed to keep cutting power steady over different spindle speeds. At low speeds they require high torque to cut, and at higher speeds the torque needed drops, while the output power stays about the same. This contrasts with loads like fans and centrifugal pumps, where torque (and thus power) tends to rise with speed, making them variable-torque rather than constant horsepower loads.