Chop saw motor issue

[rattle_snake]

I have an Evolution Rage2 chop saw that is having motor issues. The motor will turn but brushes arc considerably. Speed and torque are very low. If loaded (cutting) it will trip 20A breaker. Does not trip GCFI, so no current is going to GND.

I disassembled saw and visually inspected everything. Don't see anything odd. I'm assuming this is a compensated A/C commutator type motor. The commutator on the armature is clean. I measure the resistance of the stator from plug to brush holder with switch ‘on’ at 0.3ohms which seems OK and both sides are the same. I’m assuming that the armature is a series type. I get <0.1 ohm between each commutator bar. When measuring 180* across, I see a cumulative resistance of about 0.2 ohm. I do not see any shorts to the armature shaft (which should trip GFCI).

So I haven’t found anything wrong, but obviously something is. What to check next? Would a single broken coil winding do this?

I can’t just toss a $300 saw in the trash or throw parts at it without understanding what is going on. I have a backup 14” HF abrasive chop saw but I almost can’t bear the thought of going back to that turd.

SOLVED: shorted armature, replaced, fixed

 

[mm08822]

Are the brushes worn far enough that the springs arent providing enough contact with commutator?

 

[rattle_snake]

No, I would guess brushes are at 90%+. They look good as do the brush sleeves and contacts.

I am not sure my home equipment can identify a 'short' vs a normal armature coil winding (aka short length of decent size wire).

 

[rattle_snake]

I spent some more time measuring coils on the armature. It has about 40 commutator pads. I measured 180* across, and see that the values for the 20 pairs not consistent. I believe that the armature is the issue.

This saw has 3yr warrantee, its 2 years old. Armature is $40. I think I would cost more than that to ship to repair center.

 

[James-W]

I think you would be better off sending it in to be repaired. If you order parts and try to fix it, you may very well void the warranty. So if the parts you order don't fix it, then you are out the money the parts cost, and you no longer have a warranty. That's my thinking on the subject.

 

[rattle_snake]

I agree but I need to get this saw back in service asap, or buy something else. I used my old abrasive and plasma this weekend and results were bad enough to want to go buy replacement immediately.

So I ordered the $42 part. Otherwise I have to spend time constructing a decent shipping box, and spend $70 to ship across the country. Would be at least 2 weeks or more before it came back.
Looking at horizontal band saws...

 

[wyliesdiesels]

Manu wont cover shipping?

Shame on them...

 

[rattle_snake]

They cover return shipping only IF the issue is covered under the warrantee. I imagine if a guy made a big enough stink they would pick up the rest of the shipping.

 

[gungatim]

are you sure the springs are tensioning the brushes properly and/or the brushes aren't sticking in the motor? I have seen this a lot lately on Milwaukee and other equipment; overheating ruings the spring temper and the holder. good brushes but poor contact and lots of arcing...

just something to double check as you put it back together.

 

[James-W]

I have a friend who owns a Milwaukee drill. It wasn't working right, had a motor problem and was out of warranty. He took it back to where he had purchased it and asked if they could send it in to be repaired. He was told the Milwaukee repair place charged a flat fee of $60 to repair it. He decided to have it went in to be repaired.

To make a long story short, the Milwaukee repair place sent him a brand new drill rather than waste time fixing his old one. I suspect in the case of the opening poster, the repair place won't bother trying to repair the motor, they will either just replace the motor, or they will replace the saw.

 

[dogdog]

I think they have those megger meter to test these sort of shorts ..... something an ohm meter won't do.

 

[dogdog]

and btw the evolution Rage2 is their pro-sumer class of tools, if you are doing this for a living, I think you are better off getting their evo360HD steel chop saws... at least I was told, better motor..... I think some one post other brand of simiiar class as well... from Milwaukee or Dewalt.....

 

[nehog]

Resistance measurements don't really do much for a single shorted turn in a coil.

The problem is that that shorted turn will attempt to draw all the current that is applied to the coil (it amounts to a shorted secondary). Symptoms would be just as you describe: poor performance and excessive current draw.

I'd suggest finding a book on motor testing (an old book, perhaps something on Google?) and seeing what tests you can run. Typically you'd use a device called a growler to test the rotor.

 

[wyliesdiesels]

They cover return shipping only IF the issue is covered under the warrantee. I imagine if a guy made a big enough stink they would pick up the rest of the shipping.

So they only cover part of the saw under warranty?

You stated 2 years into 3 yr warranty...

 

[rattle_snake]

are you sure the springs are tensioning the brushes properly and/or the brushes aren't sticking in the motor? I have seen this a lot lately on Milwaukee and other equipment; overheating ruings the spring temper and the holder. good brushes but poor contact and lots of arcing...

just something to double check as you put it back together.

they seem happy. Saw went from good to bad all of a sudden.

I have a friend who owns a Milwaukee drill. It wasn't working right, had a motor problem and was out of warranty. He took it back to where he had purchased it and asked if they could send it in to be repaired. He was told the Milwaukee repair place charged a flat fee of $60 to repair it. He decided to have it went in to be repaired.

To make a long story short, the Milwaukee repair place sent him a brand new drill rather than waste time fixing his old one. I suspect in the case of the opening poster, the repair place won't bother trying to repair the motor, they will either just replace the motor, or they will replace the saw.

The motor case is integrated into the saw housing. So to 'replace' the motor would be the armature, stator and brush assembly.

I think they have those megger meter to test these sort of shorts ..... something an ohm meter won't do.

I have access to lab full of high end test equipment (7.5 digit MM, ect) but I believe I was able to find the issue with my low end meter.

and btw the evolution Rage2 is their pro-sumer class of tools, if you are doing this for a living, I think you are better off getting their evo360HD steel chop saws... at least I was told, better motor..... I think some one post other brand of simiiar class as well... from Milwaukee or Dewalt.....

I'm just guy who likes to cut big pieces of metal into smaller ones. then weld them back together.

Resistance measurements don't really do much for a single shorted turn in a coil.

The problem is that that shorted turn will attempt to draw all the current that is applied to the coil (it amounts to a shorted secondary). Symptoms would be just as you describe: poor performance and excessive current draw.

I'd suggest finding a book on motor testing (an old book, perhaps something on Google?) and seeing what tests you can run. Typically you'd use a device called a growler to test the rotor.

Yes, not going to find a single coil. The test I did was to compare the resistances of the whole armature at 180* on the pads, of each 180* pad set. This is effectively the parallel combination of both sides (180*) of the respective coils in series.
So in this case with say, 40 commutator pad, there are 20 coils in series on each half that are in parallel with the 20 on the other.

I found that the 20 measurement were not consistent. Max value was 0.2ohms, with min of 0 at 90* to the max, which makes sense give it's series/parallel construction. Note that my meter has a minimum reading of 0.3ohm with leads shorted, so my values are adjusted accordingly.

So as the armature rotates and brushes contact pads that are effectively shorted, it draws excessive current.

Yes I cheated and used to Google identify motor type, operation and test methods. As an EE, if I can't diagnose an electrical issue, I have failed in life.

So they only cover part of the saw under warranty?

You stated 2 years into 3 yr warranty...

Warrantee covers the whole saw. They only cover return shipping if the issue is warrantee-able, aka manufacture defect.

Armature should be here today so we will find out soon....

 

[nsula_country]

Dealt with this on a 9" SteelMax dry cut saw. Shorted Armature.

CT

 

[rattle_snake]

Installed new armature and saw is back in operation.
So while a warrantee is nice, in this case is was not useful to me. It was quicker, easier and cheaper to fix myself, plus I learned something.

A real English speaking person a Evolution tools quickly answered phone and my parts were shipped immediately.

From the intellectual classic Tommy boy;

Ted Nelson, Customer: But why do they put a guarantee on the box?

Tommy: Because they know all they sold ya was a guaranteed *************. That's all it is, isn't it? Hey, if you want me to take a dump in a box and mark it guaranteed, I will. I got spare time. But for now, for your customer's sake, for your daughter's sake, ya might wanna think about buying a quality product from me.

Ted Nelson, Customer: [pause] Okay, I'll buy from you.
[emoji38]

 

[dogdog]

LMFAO... so you got the box marked guarantee?

 

[rattle_snake]

Yes... The affordable Chinese made product!
Should have bought a Dewalt or Rigid for 2-3x the money I didn't have then.

Although I have had several HF tools that lived very long abusive lives.
I'm just happy to have to working again.

 

[NUTTSGT]

Well, it appears that your problem is solved. I have similar issue with my Milwaukee chop saw. When I use the outlet by the O/H door, it wants to trip the breaker. When I use the outlet near the shop bathroom, it doesn't. I'm guessing the outlet might be getting weak and it's the only thing on that circuit I believe.

 

[rattle_snake]

Well, it appears that your problem is solved. I have similar issue with my Milwaukee chop saw. When I use the outlet by the O/H door, it wants to trip the breaker. When I use the outlet near the shop bathroom, it doesn't. I'm guessing the outlet might be getting weak and it's the only thing on that circuit I believe.

Same breaker or are outlets on different ones? Trip GCFI or the overcurrent? Trip on startup or during cut?

 

[manwithtools]

Man, you guy's have missed the sberry school of electricity. You need to read and follow the below:

"I have had to add 25 ft of 16 to my chop saw to keep it from popping a breaker on starts."

"It comes factory 14 cord as do most of them. A little voltage drop doesn't hurt, it slows inrush."

Stand by, he'll be here to give you the details.....

 

[NUTTSGT]

Same breaker or are outlets on different ones? Trip GCFI or the overcurrent? Trip on startup or during cut?

Different breakers.

Overcurrent, no GFCI.

On start up.

 

[rattle_snake]

swap breakers if they are the same type/rating and see if problem follows the breaker. If it does, replace breaker.

 

[mm08822]

Well, it appears that your problem is solved. I have similar issue with my Milwaukee chop saw. When I use the outlet by the O/H door, it wants to trip the breaker. When I use the outlet near the shop bathroom, it doesn't. I'm guessing the outlet might be getting weak and it's the only thing on that circuit I believe.

Seems like you could be in the same situation as in this thread:

https://www.garagejournal.com/forum/showthread.php?t=355720