Induction Motor Failure Autopsy
Induction Motor Failure Autopsy
(OP)
Hi all.
Can you help please?A Jeary SD14/039/57 30Lbs/ins. ST rating 59 RPM with right angle worm/gear box stopped working in my absence. Replaced bearings and seal 6 months ago after the bearings became rough/stiff and the motor kept overheating and seizing after a short run. The bearings and seal where replaced and new oil in the box. Now the seal is loose on shaft and from housing. One bearing is seized and oil is everywhere and the coils cooked. Motorman, can you you help diagnose the sequence of events that led to it's demise? Can you recommend a source for rewind or replacement? It also has a gear to drive a castellated rubber belt. Question-If jammed, do (why)the coils heat up?
Thanks
Can you help please?A Jeary SD14/039/57 30Lbs/ins. ST rating 59 RPM with right angle worm/gear box stopped working in my absence. Replaced bearings and seal 6 months ago after the bearings became rough/stiff and the motor kept overheating and seizing after a short run. The bearings and seal where replaced and new oil in the box. Now the seal is loose on shaft and from housing. One bearing is seized and oil is everywhere and the coils cooked. Motorman, can you you help diagnose the sequence of events that led to it's demise? Can you recommend a source for rewind or replacement? It also has a gear to drive a castellated rubber belt. Question-If jammed, do (why)the coils heat up?
Thanks





RE: Induction Motor Failure Autopsy
You say "motor kept overheating and stalling". This only needs to happen one time to damage the motor. You should prevent that from EVER happening. Where is your overload protection for your motor?(Which also can prevent your facility from burning down.)(And is required by NEC)
After seal replacement you're right back in the same place again. This is all pointing at what the belt is driving.... The load has increased past the gear box's rating or the normal heat generating losses of the gear box have now greatly increased from scuffing gear teeth, rough surfaces, and violated lubricant.
Keith Cress
kcress - http://www.flaminsystems.com
RE: Induction Motor Failure Autopsy
Well, it became hot and there was a smell once and I tested it again to check for myself. It worked but I felt it was hot and investigated and repaired.
It was an in house installation when I arrived and there is no dedicated trip. Point taken...thanks.
I think the dry gear box originated it's demise and possibly age , the bearings?
I am there again tomorrow and they will be seeking my advice and hopeful of a solution.
I ponder as to whether the seal failed and allowed oil past the still working bearing and onto the windings and caused a short or the bearing seized and caused the heat which damaged the seal and let in oil or whatever.
Question-If jammed, do the coils heat up and why?
Thanks
RE: Induction Motor Failure Autopsy
So yes the 'coils', we call them windings, do heat up, and generally in a spectacular fashion.
If your seal failed and let out the oil then the gear box bearings, shafts, and gears could/would die.
You show up and replace the oil and the seal. But now the part of the shaft the seal rubs on can be ever so slightly rougher. After a few thousand revolutions the new seal again dies. Step and repeat.. It's a possibility.
Keith Cress
kcress - http://www.flaminsystems.com
RE: Induction Motor Failure Autopsy
No fan at all and totally sealed.
I would never have deduced that the old seal could roughen the shaft rather than polish it!
There is another clue to the problem in that the starter cap. needed help with a push on the load to get it going, but once going, if disconnected and reconnected soon after, it worked.
However, if unplugged and then replugged, it started.
I assumethe switch was single pole and that 2 pole and earth connection made the difference.
So, sometimes it was not prodded into start and that's when the coils eventually cooked.
I can only wonder why the cap. start failed after renovation.
Cheers
RE: Induction Motor Failure Autopsy
Unless the air flow stops, which happens when the rotor stops.
Mike Halloran
Pembroke Pines, FL, USA
RE: Induction Motor Failure Autopsy
bad capacitor
bad centrifugal switch mechanism
bad centrifugal switch contact(s)
Internal motor problem:
Motor bearings failed
Start winding insulation failure
Overload on output of motor
from gearbox problem
from load problem
Low voltage supply to motor
It's not that the seal will roughen the shaft in most cases, instead the groove worn in the shaft by the seal lip typically decreases the lip tension and allows oil to leak. It's also very likely the bearings failed first and then the seal could no longer contain the oil as the shaft was oscilating back and forth.
RE: Induction Motor Failure Autopsy
RE: Induction Motor Failure Autopsy
Keith Cress
kcress - http://www.flaminsystems.com
RE: Induction Motor Failure Autopsy