No, I hardly believe that they are misplaced. Anyway I will check it and see. I know because the spring is fine and look great, has force and make the brush touch solidly. The carbon brush is still very long, that's how I know it's fine.

 

If after following ALL the advice and suggestions posted so far and nothing appears to have changed and there still appears to be a problem, then further definitive bench testing may be required, via such as the Growler mentioned earlier.
Max.

 

It is likely that if the motor has short circuited windings on the rotor that the cost of repair will be more than the cost of a replacement, at least here in the USA. Harbor Freight has some great deals and they seem to be honest about the quality of the products that the sell.

 

I still have not been able to clean the tool, but I opened this thread to get info. I'm pretty sure it's not a short because apparently it looks quite clear that the sparks are coming only from the brushes, and I'd say just one of the brushes, if I remember correctly.

 

All I can say now is I hope you don't have other tools like this, that you can see into the brush area. Sparking is a very common phenomenon with brushed motors, so if you look you will see it and drive yourself nuts worrying about it.

 

All I can say now is I hope you don't have other tools like this, that you can see into the brush area. Sparking is a very common phenomenon with brushed motors, so if you look you will see it and drive yourself nuts worrying about it.

Ummm, first, it's nice that I can see it because that means the area is ventilated, and also I can check if there are problems, like excessive sparks, which seems to be the case. I'm not "nuts" or anything, I'm just seeing excessive sparking and I think it's not normal. If after a clean up, I see the same sparks, then I will conclude it's kinda broken or normal. I won't have access to the tool for a few days, that's why I wanted to read some info here about what it could be and when I have access, apply those things. It's clear that some of you say it could be normal, well, I'll take that into consideration.

 

It's clear that some of you say it could be normal, well, I'll take that into consideration.

Well practically all possibilities have been covered here.
"Normal Sparking" is relative and whether it is excessive usually comes with observational experience.
IF you feel there is a problem here, go through all the empirical testing already suggested, and see what happens.
Most severe problems comes accompanied with lower or lack of performance.
Max.

 

If it ain't broke - don't fix it. My neighbor follows that mantra religiously. He'll drive his car on worn belts and tires until something breaks or blows out. Then - and only then - will he fix it. Radiator hoses, brakes, windows that go down but won't go back up - plastic film for that case. And the pièce de résistance: putting a flag sticker over the check engine light. Geez! This kind a belongs in the jokes thread. Sadly, I'm not joking.

 

"If it ain't broke - don't fix it"
That's probably one of the most hated (by me) mantras I keep reading over and over again, and people proudly say it like it's smart or clever. I won't explain why I hate it so much.

To the point, when I get my hands on the tool, I will do some tests and may be record a video and take some pictures so you people can work in your thoughts with something real. I believe I was so sure it was a problem because the fact that the sparks only came from one carbon brush.

 

One other check while you are in to it.
If you have a digital caliper, measure the width and thickness of each brush!
Max.

 

So I finally disassembled the machine again. The commutator bars of the rotor were black, probably because of the brushes. I tried to clean it with a cloth, but the black dust was really stuck in there. So I ended up sanding it a little bit, until everything was shiny again. I also sanded a little the brushes in case there were a film or something in the contact area.

The result: the sparks are still there, but their intensity is much less. Indeed, I wouldn't refer to them as sparks anymore, it's more like a constant arcing all along the commutator, like a blue/yellow circle, not any visible spark "exploding" all over the place. So, I guess I've reached the normal arcing of the motor.

 

Constant arcing around the commutator is not right. That points toward there being copper particles stuck in what should be insulating gaps between the segments. It is also a symptom of very heavy loading, so verify that the motor spins freely when you turn it by hand with the power disconnected. If you have a means of measuring the running current, verify that the current with no load is less than the rated current on the label.

 

The only way you are going to find out is with the growler (post #22), never sand the surface of a comm, it should be done with a com stone.
I don't believe you confirmed as to if it is a Universal AC/DC wound field motor?
If so some sparking is normal, particularly in a Universal type motor, the carbon from the brushes is usually disintegrated during this arc flash.
You need to be worried when there is a circular arc is all the way around the com!
Max.

 

I sanded just the surface to make it shiny (and great) again. Otherwise it was imposible to remove the black stuff. I cleaned the commutator thoroughly, so I'm pretty sure there were no shorts between the different pairs because at the end it was all shiny and cleaned and, as far as human eyes can see, there were no copper particles joining 2 separates pieces.
What I can guarantee is that the sparks and spark sounds it did last time, after the cleanup, disappeared, and now it's like a circle around the commie without noises.
I'm sorry I can't show you a video, the machine is not in my usual place.
Can you show me a video of normal sparking?
I can't find any video guide about this.
And yes, it looks just like a regular electrical motor. I don't know if it's AC or DC. The electric jig saw directly connects to AC, but I don't know if it has inside a small transformer. I don't think so, so I'd say it's an AC motor.

 

If it has a commutator and a wound field (not perm magnet) then it is a Universal motor (AC/DC).
So has the concern or issue dissapeared now?
There should be no more than light sparking which is usually due to the minute carbon particles glowing.
The issue you do NOT want to see is blue coloured stream that almost circles the com.
If this is an old motor and you sanded the com, you probably eliminated any com bar separators from being a little high due to wear, if this does have a mica-insulated com.
Now wearable material is used..
Max.

 

Hi, I have a 300W electric saw (small), and the motor carbon brushes start sparking "like crazy" whenever I turn it on. First, I'd like to know what can cause a spark (short circuit, simple friction between brush and metal???). The brushes are really easy to take out, so I did and they look fine, they don't look burn't or destroyed. What I don't know how it is is the commutator (or armature). This is basically my motor:

Should I sandpaper the carbon brushes to remove a bad "coat"? (there's still a lot to go, and the spring is strong and nice)
May be should I sandpaper the commutator and make it shiny and uniform?
Could it be an impossible to solve problem?

Chances are your armature is out of balance, or you need to replace bearings, i had a similar problem with a polisher, the front bearing seized and the motor turned the shaft around in the bearing and the shaft got worn a bit, the slightest play on any of the bearings causes the armature to bouce the brushes away from the communtator which causes a spark, if you checked everything else, its probably bearings, and a cheap fix too, worked for me...

 

Welcome Jp joubert1975 to AAC.

This thread is over two years old. Either the problem has been fixed or whatever was at issue may have been replaced.

 

Welcome Jp joubert1975 to AAC.

This thread is over two years old. Either the problem has been fixed or whatever was at issue may have been replaced.

Yeah, it's 2 years old but the problems are still relevant in today's motors, so it's not an empty discussion. It can help others. I am still receiving updates of this thread.

I think I found the answer, yes. It's a really simple one: the saw with the motor was for 125V, and I was using 230V. How this appliance came to my hands, don't know.

It was an old electric saw, still functional but pretty worn aesthetically, and there was no info outside. Suddenly it clicked in my mind: OH GOD, this thing was designed for 125V!!!

After I used a transformer from 230V to 125V, the sparks were WAY weaker, but still there. After sanding the brushes and the rotor metal cylinder, it worked almost without sparking at all.

 

I found the answer, yes. It's a really simple one: the saw with the motor was for 125V, and I was using 230V.

Either the problem has been fixed or • • • .

Wouldn't ever think the issue is no longer relevant. I just suspected (as noted above) the TS (you) figured out the issue and have reached a resolution.

 

If the brushes have never been replaced, and it has had a fairly high rate of usage, it is likely they need replacing, especially if this is a Universal motor.
Also, due to the very high RPM for this type of motor, the bearings should be checked/replaced.
If the arc is bright blue and appears to follow the comm almost all the way around, it points to a short in the motor.
Max.

I have bright blue arc in my dc motor
How can I solve short