Most electrically driven constant-speed machines operate at speeds below _________rpm.

Question

Quizplus · Accepted Answer

Most electrically driven constant-speed machines, such as induction motors, operate at speeds below 1800 rpm. This is because the frequency of the power supply in most countries is 50 or 60 Hz, which corresponds to a synchronous speed of 1500 or 1800 rpm for a four-pole motor. Higher speeds would require more poles or a different power supply frequency. Most electrically driven constant-speed machines, such as motors or generators, operate at speeds below 1800 rpm. This is because the frequency of the AC power supply in the United States is 60 Hz, which corresponds to a speed of 1800 rpm for machines with four poles. Machines with different numbers of poles will have different synchronous speeds, but they will still operate at speeds below 1800 rpm in most cases. Options B, C, and D are all above 1800 rpm and therefore not the best choice.

Most Electrically Driven Constant-Speed Machines Operate at Speeds Below _________Rpm