Rewind an Electric Motor

Electric motors are relatively simple mechanical devices, but rewinding the coils on a DC motor is a precise task that should only be undertaken by those who with experience in mechanical or electrical repair. A mistake or poorly-performed rewind job will result in a motor that doesn’t work. At that point, your only options are to buy a new motor or to take it to a professional shop for repair. Given the variety of motors and types of windings, this can only be a general article on rewinding. If you don’t understand the terminology, you shouldn’t be rewinding a motor; once you start removing the original coils, there’s no going back.

Steps

  1. Clean your work surface to make sure it’s free of dirt and dust.
  2. Remove the motor housing to reveal the armature, stator, and the windings.
  3. Document the present configuration by taking notes or photographs. You may even wish to videotape your deconstruction so that you can precisely recreate the original winding pattern and connections.
  4. Take the wire from the tabs on the brush pads. Bend the tabs gently (and as little as possible) and completely remove the wire from the tabs before cutting the coils of the wind.
  5. Cut the coils in the wind free from the armature and/or stator. The easiest place to cut is at the tops of the coils at the top of the armature and/or stator posts. Count the number of winds in each coil so that you can rebuild the motor to its original configuration.t
  6. Check the insulation that lines the actual steel laminate areas of the stator before you rewind an electric motor. If it’s in good shape, you can put it back in place before beginning your rewind. You can replace burned or damaged insulation with similar material or insulating tape.
  7. Rewind the armature and/or stator using the same gauge and type of magnet wire that was on the original motor. If you’re more experienced, you may wish to upgrade your wire’s quality, substituting a nylon-and-polyurethane-coated wire for the original enamel-coated wire, for instance.
  8. Recreate the exact winding pattern and number of coils around each winding. Take great care to make each coil tight and precise for the best performance.
    • When beginning your first winding, leave the end of the first winding free but long enough to reach the first tab. The last winding will attach to the same point.
    • Crimp all the other windings down as you work to hold the wire in place. You do the winding with one long wire, so don’t cut anything as you go.
    • Before you crimp the wire down behind the tabs, use a sharp knife or sandpaper to remove the insulation from the wire at the point where it makes contact with the tab. Make sure you only remove as much insulation as is necessary to create good contact.
  9. Connect the end of the last winding and the loose wire you left in the first winding to the tab where you began.
  10. Check to make sure that none of the wires connecting to the tabs are touching.
  11. Reassemble the motor housing.


--199.190.45.186 18:04, 11 September 2013 (UTC)

Tips

  • Squirrel cage style stators tend to be a bit more complicated. If you rewind one of those squirrel cage stators, especially one of those that has the coils that, looking through the center of the stator, resembles a rope circle, it is best to find a piece of wood as big as the inside of the original coils, or you can also use a Dremel to sand down a slightly oversized block or stick to the proper size, and wind the coils on that stick. Then, once the coil is finished, slide it off the stick, wrap the long sides with the type of motor insulation that wraps like tape, that comes in a roll that resembles a roll of tape, insert one long side into the stator slot while leaving the other long side hanging out, repeat the process, being sure to note the direction of winding so you can insert the coils according to the required polarities, and once all coils are in, then you pivot them and insert the other long sides into the slots in the stator, wire the coils together end to end, and you're good to go. To make it easier to insert, you should wind the coils in a way that the coil is almost flat through it's thickness.
  • Practice on an old or inexpensive motor before you try working on an expensive one.
  • A/C motors are the best types for beginners as all of the wiring and windings are concentrated in the stator. On all A/C stators, whether 2, 4, 6, 8 pole, etc, every other coil is wound in a different direction. For instance, if you are winding one post in a clockwise direction and you move onto the next post, you would wind that post in a counterclockwise direction. And then the next post is wound clockwise, after that, counterclockwise, and so forth.

Warnings

  • Do not, under any circumstances, wind the new wire on the bare steel of the stator/armature posts. The coils must be insulated from the steel laminates at all times. Most vendors sell motor insulation in the form of large sheets that can be cut and sized simply with a pair of scissors. Motor insulation can also be found in the form of a wrapping tape. But be warned; it needs to be specifically designed for use in an electric motor. Regular electrical tape, duct tape, tarp tape, etc, will not work in an electric motor as it will wear out and eventually pose an electrocution hazard. The finished insulation sleeves must extend at least an eighth of an inch above the top and bottom of the stator posts and should completely enclose the wiring between all steel armature posts. Without the insulation, the pressure of the wire against the stator/armature posts can breach and/or possibly even grind away the insulating varnish on the wire, exposing the wire's channel of electricity, eventually posing an electrocution hazard and potentially even causing an electrical short. Wiring in an armature without insulation can pose an even greater electrocution/electrical short hazard as centrifugal forces that occur while the armature is spinning are highly capable of causing uninsulated wire to rub against the posts, resulting in more severe erosion and loss of the varnish insulation.
  • Be sure to use the exact same gauge wire that was originally used. Too heavy a gauge, and the motor will spin slow or not at all. Too thin a gauge and you will have overheating, and possibly even a potential fire hazard. And if you used extremely thin gauge wire, you can end up in a situation where you get smoke belching from the new windings almost right after you plug it in. Before taking on the task of rewinding an electric motor, it is extremely advisable to get yourself a wire gauge so that you can measure the gauge of the wire used in the original windings.
  • Only magnet wire is to be used in rewinding a motor. Any other types of wire (floral, arts and crafts, hanging wire, etc) will not produce any spin in the motor at all and in fact has the potential to cause electrocution and even send you to the emergency room. Additionally, under absolutely no circumstances at all whatsoever do you ever attempt to use Nichrome wire to rewind a motor! Nichrome wire is the type of wire used as the heating element in electric heaters, and if you try to rewind a motor with Nichrome wire, it would just heat up when you plug it in and it would almost instantly burn off all of the insulation and potentially start a fire. Additionally, the tremendous heat generated by windings made of Nichrome wire might cause warping, or even partial melting of the stator posts, and possibly even the housing, shaft, and rotor.
  • Before you remove the windings, you must understand exactly how the brushes, windings, and armature interact, or you won’t be able to successfully complete a rewind project.

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