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Single Phase motor issue ?

BHolcombe

Aluminum
Joined
Apr 15, 2019
I recognize that I'm at risk of posting this in the wrong location, but to be frank posting questions in 'General' slightly terrifies me.

Here goes:

I have a dust collector with a 3hp 1ph motor manufactured by Leeson, it began making an odd noise while running, sort of like a surging. On advice I replaced the capacitors, I did so with identical units to ones being replaced. Problem resolved.

A month later now the problem has returned, replaced the capacitors but that magic pill approach has failed me, and the motor continues to make the same noise.

The motor seems to function but I can't quite understand what is causing it to produce such an odd sound.

- I've checked the simple things, all is well in the electrical panel and at every connection between that and the motor. I have checked the connections at the motor. It does not sound like a bearing noise to my ear and I dont believe anything to be rubbing or stuck in the impeller.

Help would be appreciated, I'm attempting to avoid simply being a feckless parts changer and actually diagnose this to find the problem rather than chuck it in the trash and install a new one.

Rather than try to mimic the noise :D I've taken a video which I have posted on youtube.

 
The 'surging' can definitely be heard on the video you posted (nice job) and it could actually be a bearing headed to the happy hunting ground, but it surely isn't anything electrical.

What's on the suction side of your dust collection system..maybe gates at each machine? Other than a bearing going out, the motor sounds like it may be loading and unloading through some issue with the suction side of the system.

The very first move would be to isolate the motor from the fan and listen to it then. If you don't have a mechanics stethoscope, put your ear to a long screwdriver and touch it to each bearing housing on the motor as it runs.

Stuart
 
Stuart, Thanks for your reply. I did some checking just now, with all blast gates open (woodshop) the issue lessens. As I close the blast gates the noise becomes louder. In the past I have been able to run this with only one blast gate open without issue.

The airflow seems normal.

If it’s a bearing, that would be a relief as I can fix that kind of thing.

Later today I will separate it from the housing and listen to it.
 
In a dust collection fan/blower, with all gates closed, the fan sort of idles as no air is being 'pushed'. This would put the least strain on the motor and if a bearing were getting bad, it would tend to wiggle and growl more at this point. Opening a gate or allows air in which means the motor must now work to move it which would tend to load up the motor and may lessen any bearing sound.

Motor bearing replacement is cheap and easy..sounds like you've done it before. I would diagnose the motor sans fan, just the bare motor.

Stuart
 
The is not a "surging", it sounds like a "beat note", and may or may not be bearing related in terms of possible failure.

In any case, I concur that it is probably mechanical. It could be a beat note between line frequency vibration and a rotational vibration, especially if it changes the rate of repetition if you change the "gate" setting slightly.

I don't think I would be too worried about it just at the moment. I have heard that same type noise/effect before, and nothing failed. My feeling is that you will hear it get worse if it is indicating an impending failure.
 
My feeling is that you will hear it get worse if it is indicating an impending failure.

Exactly..it won't self heal and it will eventually rear its ugly head, then you'll know for sure 'who's on first'. My credo.."it'll develop".

I spent 40 years waiting for stuff to break so I could fix it. It almost always let me know when it was ready to be fixed.:)

Stuart
 
I agree with those who say it could be a bearing. I had a similar surge in a 3 phase idler that was New Old Stock. it was noisy and overheated. Upon disassembly, the bearings were found to be rough. New bearings for less than $20 cured the noise and over heating.

At least a quick disassembly to check would be in order.

Good luck.
 








 
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