Failure in 1200 kW 6 kV motor
Failure in 1200 kW 6 kV motor
(OP)
Hello All
I would like to know your inputs about this failure.
In the attachment you will find some pictures.
Thanks and regards
Carlos
I would like to know your inputs about this failure.
In the attachment you will find some pictures.
Thanks and regards
Carlos





RE: Failure in 1200 kW 6 kV motor
Gunnar Englund
www.gke.org
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Half full - Half empty? I don't mind. It's what in it that counts.
RE: Failure in 1200 kW 6 kV motor
Regards
Carlos
RE: Failure in 1200 kW 6 kV motor
Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.
RE: Failure in 1200 kW 6 kV motor
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If we learn from our mistakes I'm getting a great education!
RE: Failure in 1200 kW 6 kV motor
The stator is earthed, the wedges are magnetical
Regards
Carlos
RE: Failure in 1200 kW 6 kV motor
Observation 1 - Wedges missing. They do not appear to have moved axially out end of slots, since all remaining wedges come to the same axial distance along the end of the stator.
Observation 2 -Evidence of foreign material in airgap damaging both wedges and top of teeth (picture upper right hand corner).
Observation 3 – Some blackening of end turns connection-end upper left hand corner
If we assume items 1 and 2 are related, the obvious ties might be:
Scenario 1: Foreign material caused wedges to come loose.
Scenario 2: Wedges are foreign material which caused the damage.
I have also seen a scenario 3 where rotor contacted stator and abraded the stator tooth tops. This created a lot of localized heating which baked the wedges in that area and made them fall out. But that damage was limited to one area of the stator. And the signs of dramatic overheating don't seem evident here.
Being far away, any guess is just a guess. My swag would be scenario 2, because:
A – magnetic wedges are notorious for coming loose under vibration, especially if not vpi'd (has this machine been vpi'd)
B – the missing wedges seem very much spread out, might be expected if caused by vibration and poor retention. I would expect if the main problem was foreign material it might be more localized. Granted there is a localized area of higher damage, but ...
Followup questions:
Are there any other noteworthy visual observations not described above in observation 1, 2, 3.
Can you describe the machine type? I don't recognize the radial spoke-looking things outside the stator in the upper left hand picture.
What do electrical tests look like on stator (balanced resistances, grounded?).
Was stator core hot-spot test done.
Can you provide closeup picture of damaged area of stator core toothtops.
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(2B)+(2B)' ?
RE: Failure in 1200 kW 6 kV motor
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If we learn from our mistakes I'm getting a great education!
RE: Failure in 1200 kW 6 kV motor
On a different subject, this guy Henk has some interesting discussion of wedge-ology:
ht
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(2B)+(2B)' ?
RE: Failure in 1200 kW 6 kV motor
RE: Failure in 1200 kW 6 kV motor
----------------------------------
If we learn from our mistakes I'm getting a great education!
RE: Failure in 1200 kW 6 kV motor
----------------------------------
If we learn from our mistakes I'm getting a great education!
RE: Failure in 1200 kW 6 kV motor
I am with your theory: " Scenario 2: Wedges are foreign material which caused the damage", the wedges are magnetic type and the motor was not VPI. The problem is characteristic of windings with magnetic wedges. Some heavier, dense magnetic wedges can work loose, when the wedges fall out of the slots, with the motor in operation the wedges are contacted and fragmented by the rotor and driven right to the exposed stator coils causing a ground fault.
The pole-pass magnetic pulsation could causes it.
Regards
Carlos