Vol. Advanced Theory
Chapter More Principles of Industrial Instrumentation (Animated)

Understanding How Three-phase Electric Motors Work

The key to understanding how three-phase electric motors work is to have an accurate mental picture of the rotating magnetic field created by the stator windings of a polyphase motor. One of the best ways to visualize this phenomenon is to observe a string of “chaser” lights blinking in a polyphase sequence. Just in case you don’t happen to have a string of polyphase lights at your viewing convenience, I have provided a simulation here to demonstrate how the illusion of motion is created by the sequential energization of light bulbs.

Note how the lights appear to “move” from left to right as the energization sequences moves from A to C. After a few cycles of ABC, two of the wires are crossed to reverse phase sequence. This has the result of reversing the apparent direction of motion! It matters not which two phases are reversed. In this animation, I reverse phases A and B, but I could have just as well swapped phases B and C, or phases A and C, and created the exact same effect.