How much commutator/brush sparking, is 'normal' in a new motor?

[mickynz]

Hi, I'm fixing a portable spa for someone, the blower motor (universal) had gone. The brand new exact replacement gives off a surprising amount of sparks between the brushes and commutator. While I know sparking isn't abnormal as such, electric motors aren't really my thing and I'm not sure if this is 'normal' breaking in of a cheap motor, or something else. Mostly a generalised white blue glow, but with a few orange shooting sparks every few seconds. The commutator is already coated quite darkly.

The motors are sealed and the commutator is unreachable and the brushes non-adjustable. The previous one had large chunks missing from the armature and one of the brushes entirely eroded into carbon dust. They strike me as cheap and badly made, so I'm thinking this is sadly normal for this particular motor, but any advice from someone with experience would be greatly appreciated. Thanks.

 

[waross]

Replace the motor. The armature is probably shot.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[mickynz]

Thanks! Really? It's new, never been used. It seems very badly made though... The old one's armature was nearly in pieces.

 

[Skogsgurra]

For a DC motor of any size, this doesn't look good. But this seems to be a universal motor and they do spark - especially when run off AC.

I'd say that you keep this document (the sparking) and do nothing more. If this motor also has short life, then dig deeper. Otherwise, just let it be.

This motor is for 50 Hz. If you run 60 Hz, it will spark more.

Gunnar Englund

http://www.gke.org

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Half full - Half empty? I don't mind. It's what in it that counts.

 

[mickynz]

Thanks! I think I'll do that. It does look pretty bad. I wish I could open it or adjust the brushes or even just test the brushes are moving in the holders properly, but it's all riveted shut.

The last motor was a mess and by all accounts this brand of portable spa die on a regular basis, so I'm thinking it's a really badly made motor (let alone the spa pool, which is horrific design incarnate).

I found a guide on spark characteristics and motor life, it seems to suggest it may get a couple of hundred hours out of it at least, which would be about the life of the last one at a guess (and all the others I've heard horrible reviews about). I just find it disappointing something could come that badly made.

Thanks for your help!

 

[Skogsgurra]

It all depends. If it is consumer goods, the life expectancy won't be more than a few hundred hours. Quite normal.

For small hobby tools, the L10 life of bearings is no more than a few hours. Some fail after a few hours but the majority live a lot longer than that. You cannot use normal industrial standards for consumer goods.

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[waross]

I apologize. I misread your original post and thought that you had just replaced the brushes. I agree with Skogs advice.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[Skogsgurra]

We always agree, Bill!

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[WoodrowJWeen]

My 30 year old vacuum cleaner and 25 year old drill both have universal motors and have always had a fair amount of sparking. Both still going strong. Haven't replaced the brushes yet.

 

[mickynz]

Thanks for all your advice. Woodrow, that's comforting to know! Most of my experience is with things I've made myself or repairing less mechanical faults, motors are fairly new territory for me as I never use them in things I make.

I can't for the life of me find that sparking formula now. It was a rough approximation for brushed motors in general. Something along the 'ideal' life of the motor in hours, divided by an ascribed value based on the level of sparking. Less than 1 for an excellent low/no spark set up, to 50, for a Catherine wheel of a motor. So 7000 hours 'expected ideal' divided by 50, would reduce its life expectancy to maybe 140 hours at best. There's so many variables it's not that valuable, but it seemed to suggest horrible sparking sadly isn't unexpected. Like I said, a few adjustments may help, but it's sealed.

Commutator wear charts are everywhere, there should perhaps be more 'acceptable level of sparking' charts? It only gets commonly referenced as a fault, but unfortunately seems a real world event there could be better guidelines on.

Anyway thanks again, and best wishes for the holidays!

((Oh and our supply here is 50Hz, I had to get the motor from the UK as they ended up being the only place on the planet with one. That spa could win an award for bad design, most people seem to need an average of 3 total replacements. Horrible thing. I don't even like spas. It's in danger of being beaten to a state requiring more than a new motor.))