When operating at different speeds, a motor may be required to deliver ___ to a driven load.

When operating at different speeds, a motor may be required to deliver ___ to a driven load.

• A. Any of these
• B. Variable horsepower
• C. Constant torque
• D. Variable torque

Answer: (A)

When a motor drives a load and the speed changes, the amount of torque and power the motor must supply depends on how the driven load behaves. Some loads require roughly the same torque at different speeds (constant torque), so horsepower rises with speed. Others require torque that changes with speed (variable torque), such as fans and pumps where the load increases rapidly as speed increases, causing horsepower to rise even more quickly. In some cases, the horsepower demand itself varies with speed in a way that isn’t tied to a single constant torque profile. Because a driven load can exhibit any of these behaviors, the motor may need to deliver any of these forms of output.

When a motor drives a load and the speed changes, the amount of torque and power the motor must supply depends on how the driven load behaves. Some loads require roughly the same torque at different speeds (constant torque), so horsepower rises with speed. Others require torque that changes with speed (variable torque), such as fans and pumps where the load increases rapidly as speed increases, causing horsepower to rise even more quickly. In some cases, the horsepower demand itself varies with speed in a way that isn’t tied to a single constant torque profile. Because a driven load can exhibit any of these behaviors, the motor may need to deliver any of these forms of output.