Brushed motor with excess brush arcing

[m_c]

So I took a gamble on a used Clarke Planer Thicknessers being sold as spares/repairs.

Tried switching it on, and the motor tried to run with lots of noise briefly before the over current tripped.
Stripped the motor out, and lots of sparking was evident.

Brushes didn't look too bad, but the commutator was pretty black looking, so dismantled the motor.
I was expecting it to have been burnt out, but it visually looked and smelt fine, with the copper/resin looking good, so chucked the armature in the lathe, took a skim off it, and rebuilt it, but it made no difference.

(this was before I went around cleaned the swarf out the slots)

I have priced a new motor, but at £200, I'd be as well buying a complete new machine!

So I'm now wondering what would actually cause the excess current draw/sparking?
There is a filter fitted, and I've not disconnected anything to check for continuity yet, but could the filter cause the problem?



I could probably fit a different motor, but I'd need to work out it's speed first, as there are no markings on it.

 

[Erie Fred]

When you put the brushes back in, was there still some wear left in them ?
I.E. Could they still slide further down the brush holder channel before hanging up ?

Are they moving freely in the brush holders ?

Did you sand them in to fit the comm ?

 

[eddie49]

The filter will not cause the problem. A defective filter will just smoke, swell, split open and smell bad.
Although it may not look it, there must be shorted coil(s) on the armature. One way to tell would be with a "Growler".

 

[frank horton]

plenty of used motors about...£25-50 is plenty...their web site will tell what HP it is....
a photo of the brush gear will tell the experts on here if it 1500 or 2200rpm...

 

[RichardM]

Use glass paper and a broken hacksaw blade to clean the commutator and slots (not emery).

 

[Pigeon_Droppings2]

I had a washing machine motor with similar issues...tested fine with my little multi meter but....

After digging around online I concluded that to test the coils properly I needed a proper 240v setup. They need to be tested at operating voltage and I only had a small 9v multi meter.

In my case I suspected the insulation had broken down.

 

[Kram]

While the brushes may look fine, they could have worn down enough that the spring is not providing enough force for good electrical contact. If they have been arcing, the spring will also have got hot and could have lost strength.
I got some cheapy oversized brushes from amazon and cut them down to fit as I couldnt find the exact size. That fixed my chinese lathes motor until I decided to upgrade to a 3ph motor and vfd.

 

[m_c]

I do wonder if it's got a short.
Brushes weren't the best looking, with the corners blown off, but still had a decent enough looking contact surface.
Plenty length/spring force left on them as well.

@frank horton this motor will be in the 10-20'000rpm speed range given the gearing.

My random thought last night, was could I fit a 1.5KW water cooled spindle in the body with a VFD, as they could be had for reasonable money and would eliminate a lot of noise as well.

 

[Pete.]

It'll be a cooked winding. They get hotter internally so even if they look OK on the outside chances are that several turns are shorted inside.

 

[brightspark]

once they start arcing the commys goosed . shot it in the bin and move on

 

[Jack_K]

How did you chuck it in the lathe?

 

[m_c]

How did you chuck it in the lathe?

Pulley in the three jaw, with the commutator end supported by a live centre.

I figured given the length of it, even if the chuck end is out a few thou, it's going to make negligible difference to skimming a bit off the commutator when it's being supported the same way it would be when made. Just took a light skim to start with, and the cut was even with no high/low spot, so took just enough off to get it all shiny looking.

 

[Jack_K]

Pulley in the three jaw, with the commutator end supported by a live centre.

I figured given the length of it, even if the chuck end is out a few thou, it's going to make negligible difference to skimming a bit off the commutator when it's being supported the same way it would be when made. Just took a light skim to start with, and the cut was even with no high/low spot, so took just enough off to get it all shiny looking.

That's fine. I was making sure you didn't put the armature core in the chuck.

As others have said, it should then be undercut.