We recently collected a 200 KW Motor from one of our Customers which had failed while in service, we were asked to provide a report on our findings to see what has caused this failure.
From our findings after inspection it appears that the Non Drive End Bearing has failed which has caused the Rotor to drop on the core lamination pack which in turn has allowed the lamination teeth to cut into the winding insulation. This has then blown the winding. Also with the Bearing failure it has worn the Bearing retainer Bore on the Non Drive End. This has also resulted in shaft damage on the Rotor Assembly. Also there is some thread damage on one of the fixing holes which has been caused by vibration.
You will see from the photographs the failures that have occurred with the Motor
PICTURE 1: Stator Damage
PICTURE 2: Rotor Damage
PICTURE 3: Failed Non Drive End Bearing
PICTURE 4: Worn Drive End Bearing
PICTURE 5: Damaged Non Drive End Shaft
PICTURE 6: Worn Bearing Retainer Bore
PICTURE 7: Damaged Fixing Hole Thread
We would presume with the amount of damage that has occurred this Motor had been failing for some time.
It is so important to check that large Motors are installed correctly and have regular maintenance checks to prevent this kind of failure.
Lubricating the Bearings at regular intervals would have helped this situation but also it is imperative that the Motor Protection is set correctly as with this kind of failure the running amps would have surely risen and if the Motor Protection was correct the Motor would of tripped before the failure became critical.
On this occasion with the amount of damage to the Motor it was more cost effective to supply a New Motor rather than repair.