How to Reverse AC Motors

November 10, 2017

Motor rotation is essentially created by the manipulation of wires and magnetic fields. Thus, you can often reverse AC motors by switching the wire connections. This is as easy as unhooking and re-crimping the designated wires. (Note, not all AC motors have the ability to be reversed, but all of Groschopp’s AC motors can be).

Understanding AC Motor Rotation

Before we discuss how to reverse an AC motor, we must first understand how the induction motor rotates. For a quick explanation on how AC motors operate, checkout our Tech Tip Video.

For this example, we will use an AC motor that has two copper windings within the stator—a main winding and a starter/auxiliary winding. Each winding is comprised of a bundle of copper wires that carry electric currents and produce magnetic fields. The starter winding is typically composed of a smaller wire, resulting in a bundle with less magnetic strength than the main winding. The resulting electromagnetic activity is what is responsible for energy generation and for keeping the rotor in motion.

The main and auxiliary windings sit perpendicular to each other, creating both a vertical and horizontal field. Each winding fights to have its own charge acknowledged—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.

Reversing an AC Motor

Find the wires exiting your AC motor

AC motor wiring diagrams are available for all of our induction motors, but we will explain how to reverse the motor throughout the rest of this post.

In order to reverse the direction of an AC motor, 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 the motor to run in reverse rotation.

This easy switching of wires works because the polarity of the magnetic field is reversed, thus reversing the motor.

Switching Blue and Yellow Wires

Switch blue and yellow wires to reverse the motor.

Groschopp typically uses a standard 4-wire setup with black-yellow and red-blue connections. In order to invoke reverse motion in our motors , the blue and yellow lead wires need to be swapped. This will result in red-yellow and black-blue connections. There may be additional black wires if the motor is connected to an encoder or other accessory item. These wires can remain as they are.

How to use the Motor Search Tool

Narrow your search by selecting motor type, gearbox, voltage, and phase options for your desired motor.

Select a dominant variable: choose one of the three parameters to narrow your search. The selected variable determines which slider bar you will be able to manually move.

Use the slider corresponding to your dominant variable to further narrow your motor selection. The other sliders will automatically move to show available ranges based on the range of your selected variable.

Results will upload as your search criteria changes. If you have any questions regarding your results or how to use the search tool, you can chat with us using the green tab on the left-hand side of your screen.


Note: Groschopp Universal motors are custom built to fit your application so no additional options are available to narrow the search. Selecting the Universal motor type will prompt a message taking you to the Universal product page.

Not sure what you need?

One of our team members would be happy to help. Contact us at 800-829-4135 or by email at sales@groschopp.com. You can also chat with us using the green tab on the left side of your screen.

send us an email

Universal Motors

Groschopp Universal motors are custom built to fit your application so no additional options are available to narrow the search. Standard frame sizes and motor features can be found on the Universal page.

go to Universal page