For a quick, step-by-step tutorial on how to manually reverse an AC motor without a toggle switch, click here.
The Reversal Process
Most of us probably know at least one individual who’s quirky and backwards enough to receive the description that they “seem to have a few wires crossed somewhere.” Maybe you’ve heard the saying, (maybe someone has even said it to you), and then again, maybe you haven’t. Regardless, the point lies in what the analogy implies:
Motors naturally create forward movement, but the crossing of wires can reverse that motion. Think of washing machines, blowers, and many industrial applications—before you even use them, you can probably visualize the energy flow and the resulting movement they produce.
So how do we apply this to an AC motor?
To transform reverse motion into more than just a mechanical fluke or a light-hearted joke about particular personality trait, we cross wires, literally this time. Each motor should be labeled with specific instructions dictating which color of wires should be crossed in order to achieve reversed motion.
In other words, the instructions are on the box and reversal is a matter of cutting and re-crimping designated wires.
In this case, the blue lead (from the start of the main winding) and the yellow lead (from the end of the main winding) should be swapped to invoke reverse motion.
This works by transposing one end from the main winding and one from the other end of the main winding, because the polarity of the magnetic field is reversed, thus reversing the motor. (However, it is also good to note that some motors are nonreversible—they often combine wires in order to conserve costs, which eliminates some of the endings necessary for the reversal process.) Groschopp typically uses the standard 4-wire setup.
A rough wiring diagram of a permanent split capacitor motor might help you visualize this more clearly:
As you can see, this AC motor has two copper windings—a main winding (M) and a starter (or auxiliary) winding (S). These copper bundles carry the electric currents that produce magnetic fields—the starter winding is typically composed of a higher gauge (smaller wire) and as a result, the magnetism produced is of less strength than the main winding. The resulting electromagnetic activity is what is responsible for energy generation and for keeping the rotor (R) in motion.
Welcome to your energy hub. The magnetic fields from the windings create both a vertical and a horizontal magnetic field (one from the main, one from the starter). Because they sit perpendicular to each other (picture a plus sign from math class or an intersection sign from down the street), each fights to have its own charge acknowledged—so, right when the rotor aligns with the one magnetic field, it is then pulled an additional 90° in attempt to align with the second one.
This is what keeps the rotor spinning once it has started. It’s like the age-old image of the horse and carrot—the goal is always just out of reach, so the process continues. Just when the pull of one field almost reaches its maximum, the neighboring one overtakes it.
Similarly, to go the other way, the magnetic fields must be altered to provoke movement in the opposite direction. Since each wire consists of a positive and negative current within the magnetic fields, the flip-flopping of main and starter wires causes a reverse rotation.
For a quick Tech Tip on AC motors, find an additional video by clicking here.
For access to wiring diagrams to our AC motors, simply go to our products page, select your motor, and find the “Wiring Diagram” PDF attachment symbol located in the gray “Product Specs” box on the right side of the page.
