Electronics > Beginners

Question about DC motor failures

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ArthurDent:
Everything has a life expectancy and it looks like the fans that are failing have reached theirs. I have had to replace many fans when the lubricant dried out and there was steel to steel contact in the bearings producing the reddish iron oxide that you see. If the fan stops then the stalled motor is just acting as a heater and if the temps get too hot the plastic housing/blades can soften and distort.

The best plan would be to have a maintenance plan so the fans are replaced on some schedule to try to prevent this from happening at the most inconvenient time. Check when the units were bought and figure how long it took for the fans to start failing then start a maintenance plan to start replacing the fans at, say, 75% of that time when you can schedule a planned downtime.

dkuhn:

--- Quote from: ogden on August 27, 2018, 05:28:02 pm ---
--- Quote from: dkuhn on August 27, 2018, 04:50:56 pm ---Thanks in advance to anyone that can hopefully lend some light on this! (Total newbie when it comes to electrical things, apologies if I didn't include enough info)

--- End quote ---

Rule #1: do not 100% trust manufacturer excuses explaining failures. They will try to save their reputation by all means, putting blame on anything but themselves. Provided reason of failure can be complete BS or maybe not. Only manufacturer knows, but they will not tell you anyway :)

They say:

We have redesigned and tested the switch with new fan hardware that is both more powerful and quieter than the previous component that caused issues.

It is obvious that fan they uses fails prematurely and they had to pick another one. End of story.

--- End quote ---

Totally get this.  I'm more curious about the actual failure mode.  When I pull one from production, I'd like to tear it down and send the part to someone who knows more about it to figure out what actually caused it to fail so we can get some unbaised information.  This effects tens of thousands of businesses and will incur significant costs to remedy (travel, etc) and I'd like to have a specific failure mode to justify it other than "it failed, again".


--- Quote from: ArthurDent on August 27, 2018, 05:29:52 pm ---Everything has a life expectancy and it looks like the fans that are failing have reached theirs. I have had to replace many fans when the lubricant dried out and there was steel to steel contact in the bearings producing the reddish iron oxide that you see. If the fan stops then the stalled motor is just acting as a heater and if the temps get too hot the plastic housing/blades can soften and distort.

The best plan would be to have a maintenance plan so the fans are replaced on some schedule to try to prevent this from happening at the most inconvenient time. Check when the units were bought and figure how long it took for the fans to start failing then start a maintenance plan to start replacing the fans at, say, 75% of that time when you can schedule a planned downtime.

--- End quote ---

These devices are less than a year old across the board.  This is a new model they released that have premature fan failures across the entire line.

ArthurDent:
"These devices are less than a year old across the board. "

That isn't old age, it is a manufacturing defect. It sounds like the fans were not properly lubricated. I thought you were going to say the fans were running 24/7 for several years. That failure is not acceptable.

dkuhn:

--- Quote from: ArthurDent on August 27, 2018, 06:55:47 pm ---"These devices are less than a year old across the board. "

That isn't old age, it is a manufacturing defect. It sounds like the fans were not properly lubricated. I thought you were going to say the fans were running 24/7 for several years. That failure is not acceptable.

--- End quote ---

Yeah, they're doing the right thing and replacing every device, but I'm still curious as to what the specific failure mode is which I imagine we won't know until a teardown of a defective unit is done.

ogden:

--- Quote from: dkuhn on August 27, 2018, 07:22:45 pm ---I'm still curious as to what the specific failure mode is which I imagine we won't know until a teardown of a defective unit is done.

--- End quote ---

Exactly. You can leave one unit and wait till it's fan fails, then tell us all what exactly failed  :-DD

You see?  - We, sitting where we are, cannot tell whats wrong with those fans, unless we buy faulty equipment and inspect. Obvious failure of fans - shitty bearings.

[edit] In short about actual most probable failure mode: bearings.

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