DC motor armature winding question

[tundrawolf]

Hello,

I am rewinding the armature for a burned up winch motor. This tutorial ( http://scootersupport.com/motorrewind.htm ) shows basically the exact same motor (but for scooters). The picture

shows the armature.

My question is, please help me to understand- each coil around the armature is 5 channels wide, so wouldn't the route be 1-2-48-4 instead of 1-2-3-4, because 2-4 makes only 4 channels, when there should be 5?

 

[jim hardy]

i suggest you unwind the old motor carefully and understand how it was wound, replicate that pattern.

there's various schemes - "lap" or "wave" wound

and it might make more than one turn before returning to next commutator segment.

 

[vk6kro]

The diagram below shows what happens to the wire when it goes through the slot to the other end of the armature.

In fact, each coil skips two channels and comes back in the third one clockwise from its start.

Start from commutator slot 1 (at the top) and work around following the arrows.

http://dl.dropbox.com/u/4222062/armature%20winding.PNG

 

[tundrawolf]

Than you very much for the information. The problem is that the wires were so burned up, I managed to get an idea on how the wires were wound, but that's about it. I know that in my particular motor, I had 8 wraps of wire par coil, and each coil was spread across 5 channels, using two channels with 3 empty channels in the center.

vk6kro, thank you for taking the time to draw that. Looking at it like that, my armature is a little different. It looks like my coils use 5 channels, and this drawing uses only 4. I will have to adjust for that.

 

[vk6kro]

This isn't your armature?

The idea should be similar, though.

If you take the loop between points 2 and 3, there would be a number of turns of wire down the same two channels before it makes a connection at each end.

However it is usually a simple pattern repeated many times, so you may be able to salvage enough of your winding to rewind it. It doesn't matter that the wires were burnt, you can still work off the copper.

Good luck. Rewinding motors is a fast track to insanity.

 

[tundrawolf]

I am starting to see that! I have a very similar armature out of a small starter motor but it looks like it has 2 different wraps, one going one way, and another going the other way, instead of wound in one big rotation.

I did try repairing the burned up wires. It worked, actually, for about a second, then the rotational force of the armature threw the wires into the magnets and tore it up. It still worked, though even after that.

 

[jim hardy]

indeed vk6kro speaks truth. it will be a repetitive pattern.

the end view drawing is handy

but it might be useful for you to make a linear drawing, if only to crystallize it in your mind.

take a LONG sheet of paper - i use freezer paper, plastic on one side and white paper on other

- and draw all the slots of your rotor as if you had unwrapped (skinned) it and nailed the skin to a plank. add commutator segments as in a top view...

now start drawing your wires as you found them on the rotor , from commutator through whatever slots it traverses back to commutator, and your 5 slot pattern should soon emerge.

it will be a very regular pattern .

successful rewind deserves an award - a set of wings or something.

old jim

 

[jim hardy]

I did try repairing the burned up wires. It worked, actually, for about a second, then the rotational force of the armature threw the wires into the magnets and tore it up. It still worked, though even after that.

yes - it's important to secure the conductors against movement. i used spar varnish and braided dacron fishing line - not the cheap monofilament but good tournament line, 40 lb i think. just be aware that the actual force is pushing on the conductors, that's why they're wound tight and in bigger machines held by blocks. i used thick marine varnish sort of as a filler to make a solid mass of the windings and the fishing line as wrap around ends to hold them in against centrifugal..

i notice your picture has sixteen rotor slots and four brushes.
you said in your armature the coil spans five slots? Maybe there's twenty slots, 5 per brush vs 4? look for the rhythm in how it's wound.

I have a very similar armature out of a small starter motor but it looks like it has 2 different wraps, one going one way, and another going the other way, instead of wound in one big rotation.

do some research on lap vs wave wound , it sounds like that's what you're seeing.

old jim

 

[vk6kro]

Another essential trick is to make a wooden (or other) template to wind your coils on.

This allows you to wind the coils outside the motor and just press them into position.

Winding coils directly into the slots runs the risk of scraping the insulation off the wire in places and causing future troubles with short circuits, corrosion and arcing.

When you pull it to bits, preserve all the little bits of insulation you can. Especially the ones that go across the top of the gap to stop the coils spinning out and hitting the field coil metal.