How do I find the fault

[Lykle]

Hi All,
I have an X2 mill with a variable speed motor. I was using it with a slitting saw. It was hard work for the mill as it does not have a lot of torque. The motor was getting quite hot. I was almost done when the motor stopped.

Now if I apply power it hums and a few sparks fly between the brushes and the rotor. The brushes are more than long enough. The rotor will rotate freely without power, but with power you feel resistance.

So now I am trying to figure out what the problem is. I opened up the motor and it looks ok, no molten wires or such. I had a look at the control unit, same thing there, no visible damage.

So what do I replace? I can't figure it out.
Any help out there?

Thanks in advance
Lykle

[John Rudd]

Disconnect the motor from the control board first.....(make sure you unplug the mill from the mains please.... )
Now take 100 watt light bulb and connect that to the control board(in place of the motor)
Power up and see if the bulb lights up as you advance the pot....
If that works, you have a duff motor....sparks coming off the comm sounds like some of the windings have gone open circuit.....you could check with a Dvm on ohms range.... But try the bulb first and report back....

[tom osselton]

I had that happen (or similar) the motor got hot enough to melt the epoxy holding the brushes in place  I epoxyed it back up and have hade no problem since. 

And if you ask the wife / gf  to find the fault they point to us!

[Lykle]

Hi Guys,
Thanks for the comments.
Did the bulb test and yes it shines.
So the conclusion is that my motor is melted inside.

This is what I expected. The pully is on so tight that I have been unable to remove the rotor for now.
So that is the next step. I will see if I can get the motor rewired here, this feels like a country where they still rewire motors. Finding the right shop is the issue.

Or else, I found a replacement part for 100 pounds UK. Shipping will be hefty, but now I have nothing, right?

OK, Pully next and more reporting back to you.
Thanks guys

Lykle

[John Rudd]

Use a hot air gun to warm the pulley then pull it off the motor shaft....

I'd guess that your motor is wound for 110v ac supply to your machine?
Importing from the UK may not be the best thing....Where are you located?
Ahh...I see, you're in Limassol.....I think the mains there is 230 v, so you should be ok importing a spare from the UK

[boatmadman]

One last check before replacing the motor - are the grooves in the commutator ring clear? If they have filled with carbon from the brushes you can get these symptoms.

To clear them, just use a junior hacksaw blade to scrape out the gunk.

Ian

[lordedmond]

Then do a proper drop test on the armature.

If you are not sure how to do it google is your friend .it can be a bit dodgy to do so I will not describe it here

Or use a growler to test for shorts

But sparking is a OC some were

Stuart

[awemawson]

Stuart,

You gave me a funny turn then - I thought why drop the bally thing 

We used to do 'drop tests' on equipment destined for rockets and satellites. Steel frame with rails and drop the item onto aluminium honeycomb to give a controlled crush and controlled deceleration   

OK I now realise you mean a VOLTAGE DROP test 

[lordedmond]

Andrew

Its a thing when you have done winding for a number of years you just use the term of the trade

you are correct volt drop between segs with a dc voltage about 2 volts at 180 degrees  but lap and wave test different

we used to call the growler by another name that is very not PC nowaday  all I will say its very bad slang for a coloured person and leave it at that


IMHO  if the motor is in doubt get a new one its not worth the trouble for a easy procured part

I think if the OP lives were the ac volts are 110vac then the motor will be 90vdc and hear they are 180vdc

Stuart

[Lykle]

 

Well, I ordered a replacement motor from Arc Euro trade, gave my correct address and received it within a few days. :-)

First of all, it is not a direct replacement, mounting holes are different, the shaft is smaller and the outside diameter of the motor itself is larger than the one I had.
All issues that can be fixed easily. I will have to make a new pulley wheel as I do not want to shim a 10 mm hole to a 9 mm shaft.

Only point that is bugging me now is the following. Every time I switch the motor on, I hear a hum. I don't think I heard it before, with the old motor until after it crapped out. If I turn the POT meter to just beyond the click, the motor does not turn, it just hums. Then as I rotate to increase the revs, it starts to turn, but the hum never changes.
Is this normal? I can't remember hearing it before, but of course now I am a bit focused on the damn thing.

Thanks

Lykle

[John Rudd]

Lyle,
What speed controller do you have fitted?
I thinking it's the KB unit, if so you nay need to adjust the trim pot on the board marked MIN, adjusting it slightly (one way or 'tother ) will move the starting point  at which the motor begins to turn (or hum.....).....you may even need to adjust the MAX trimmer to achieve the same speed as before....Differences in motor characteristics.....

[lordedmond]

Lykle

what is your mains voltage ?

if you are on 240 vac  and use a phase and neutral system as we do in the UK

you say the motor is not a bolt on replacement have you got the correct motor for your machine  the new ones are brushless and will not work on the old controller for one thing they are a different voltage is the new motor black or finned ali

I know from your other posts you have a brush motor and you need the black one

Stuart

[Lykle]

Thanks John, I will have a look at the Pots.
That probably is it. I think that will also solve the fact that the motor wants to turn a little after I switch it off.

Stuart, thanks, yes I have the black one, with brushes. It runs fine, no issues there, it just hums. As I said, it probably is normal, but I am so focused on the motor now, that maybe I hear it now where I didn't notice it before.

Cutting ability seems to be better than the old motor, so i am happy there.

Lykle 

[lordedmond]

Glad you have the correct one

the hum may just be a poor varnish soak which would douse a loose lamination

to do the varnish ( its not really varnish but a heat cured thin epoxy ) that the stator armature is doped in under a vacuum then stoved to set it

it use to be the apprentice job before you when on to winding per say

Stuart

[Lykle]

Final update

Yep, tweaking the Pots helped a lot.
No more hum at the start and now I also get a lot more revs out of the motor.

Happy with the result, thanks all you guys. It has been a great help.

lykle

[John Rudd]

Final update

Yep, tweaking the Pots helped a lot.
No more hum at the start.
Happy with the result
lykle

I love a happy ending....

Glad you got it sorted....