The Basics of AC Motors
New to the industry? Trying to get a feel for how some of the basic gear in automation works?
Here’s your rundown on an important machine in your line of work: The AC motor. To get far in industrial automation, you’ll need to know how AC motors operate, when to use them, and a few basic troubleshooting tips.
Meet the AC Induction Motor
The workhorse of many industrial applications, AC motors are so prevalent that they account for a significant portion of all energy usage in the United States, and are by far the most common motor used today.
The main purpose of the motor is to convert AC electrical energy into mechanical energy. The end result is a mechanical rotary that can be harnessed to do all sorts of heavy lifting.
The “induction” part of the name refers to the phenomenon that involves two sets of wire coils, usually copper or aluminum, which are energized to produce current. This is known as electromagnetism, and the force behind it is called induction.
To keep maintenance requirements low, most AC induction motors strive to have as few moving parts as possible. These motors are found in numerous applications, such as trains, pumps, compressors, and dishwashers.
The Parts of the Motor
Now that we have explained how the motor works generally, here’s a deeper look inside.
Keep in mind that an induction motor is a type of AC motor in which power is generated by a rotating cylinder that produces electromagnetic induction.
The main parts involved in this process:
- Rotor. The rotating shaft.
- Stator. The part the generates the field and turns the rotor.
The poles of the magnets are aligned such that each magnet faces toward the center of the entire group. Then, the copper wire is wound clockwise and counterclockwise, respectively, around each pole in a north-south arrangement.
When current runs through the wires, they create a “directional flux,” which changes every half cycle, creating an alternating magnetic field, or AC current.
AC induction motors can travel at different speeds to accommodate different power frequencies. Because the United States power grid runs at 60 hertz, U.S. motors are set to this speed.
Why Use Induction AC Motors?
So why hasn’t technology displaced the humble induction motor by now? The machines have stood the test of time, mainly for the following reasons:
- Cheap to manufacture. The market for motors is very mature, so the supply is strong and abundant.
- Low maintenance. Most motors have few moving parts, especially in squirrel-cage induction motors.
- Robust. The motor can withstand most environmental conditions because it is so sturdy.
- Efficient. The full load of efficiency ranges from 85 to 97 percent.