How does motor horsepower relate to the load?

• A. The motor horsepower must be greater than the load horsepower in all cases.
• B. Horsepower indicates mechanical power; the motor must meet or exceed the load's horsepower to avoid overload.
• C. Horsepower has no relation to load; current determines overload.
• D. A motor with higher horsepower always uses less energy.

Answer: (B)

The main idea here is that horsepower is a measure of mechanical power—the amount of work the motor can do per unit time to drive the load. To avoid overload, the motor must be able to supply at least as much power as the load requires at the operating speed, with some margin for start-up and efficiency losses. If the load needs more power than the motor can deliver, the motor will be overloaded, overheat, or stall.

In practice, you select a motor whose horsepower rating is equal to or greater than the load’s required horsepower. The exact horsepower needed can vary with speed and load conditions, and starting can demand extra torque, so having a bit of headroom helps.

Note that higher horsepower doesn’t always mean less energy use; energy consumption depends on the actual load, operating speed, and motor efficiency.