ISA Certified Automation Professional (CAP) program

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Certified Automation Professionals (CAPs) are responsible for the direction, design, and deployment of systems and equipment for manufacturing and control systems.

CAP question

An example of a load that would require a constant horsepower/variable torque motor is _______________?

A. Paper roll machine
B. Clock
C. Fan
D. Conveyor

CAP Answer

The answer is A: "Paper roll machine".

As a paper roll machine winds up a spool of paper, work is done on a varying diameter with the tension and linear speed of the material remaining constant.

Although the speed of the material is kept constant, the motor speed is not. The motor starts at high speed to maintain material speed while torque is kept at a minimum. As material is added to the roll, the motor must deliver more torque at a lower speed. Torque and speed constantly changing, while horsepower is fixed.

Reference: Trevathan, Vernon L., A Guide to the Automation Body of Knowledge, 2nd Ed., 2006