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How to Select an AC Motor

AC Motors are beautiful for their simplicity: they keep moving parts to a minimum, they work on some of the simplest, most time-tested principles in engineering, and they can be counted on time and again. With that simplicity, though, comes a drawback: they cannot do much else than they are designed to. Accordingly, it is critical to choose a motor that accurately meets your systems requirements. There are three things to keep in mind in particular the operating speed of the system, the required torque, and the permissible inertia.

Operating Speed

AC motors, as reliable as they are, are all more or less one-trick-ponies, they can only run at one speed. That means that any four-pole motor you buy will always run at 1,800 rpm under no-load conditions, any six-pole at 1,200 rpm, and any 2-pole at 3,600 rpm. To find the right motor, you need to calculate your systems operating speed, select the motor closest to that speed, then, make up the difference using gearheads. Keep in mind that a motor under load will operate slightly slower, usually around 6 to 12 percent, than a motor under no load.

Torque & Inertia

Next, you will need to flesh out your required torque. While you can sometimes actually measure this with a torque wrench, you will likely need to sit down and do the calculations. Keep in mind, that for most induction motors, starting torque will actually be lower than what it is rated to, so, select a motor based on its starting torque for optimal performance.

With all of those calculations in place, it is time to select a motor and gearhead; once you have a combination picked out, double check to ensure that its permissible inertia is higher than the actual load inertia of your system.

Contact Your Motion Systems Specialists

Once you have picked your motor, we will bet you need a servo to accurately and effectively tell it what to do. And you are in luck, because we have some of the best in the business. If you have questions on how ESI Motion can fulfill your high-performance, extreme environment motion control system needs, we are always happy to answer them. Feel free to check out some of our complete servo drives, or find out more about the industries we supply. We cannot wait to hear from you, and we look forward to helping you build a system that works every time, no matter the circumstances. Contact us today by calling 1.800.823.3235.