motor failure with locked rotor
motor failure with locked rotor
(OP)
i have had two failures with single phase capacitor start motors connected to a conveyor. the motor is wired 22o volt through a drum reversing switch. in both failures the rotor was locked when the motor was disconnected from the gear reducer. the reducer and drive chain spin free when the motor is not connected. when new motor is installed machine runs normally and amperage reading is below full amp rating. is the failure due to end user overloading conveyor or is there another electrical cause such as reduction of voltage by power utility ?





RE: motor failure with locked rotor
Did the motor fail electrically or mechanically? (in other words, why was the motor rotor locked up?) a bearing failure? electrical failure internally? what type of coupling is used (& how does it look after a failure)? how is the coupling aligned?..
Is the customer giving you all the information on the loading of the conveyor? who has access to the drum reversing switch and how is it used when the conveyor is running? does the customer monitor the motor temperature at all during operation?
RE: motor failure with locked rotor
RE: motor failure with locked rotor
thanks for responding the motor in question is a c face mount, tefc the shaft when examined shows no remarkable damage and its' removal from the reducer quill is easy ... there is no smell of burnt insulation and yes the failures occurred on the same conveyor the customer of course is not monitoring the temperatures the conveyor is used to bring product from a street level loading area to the basement the conveyor is used by a wide range of personnel. there is starting and stopping under load but this not unusual for this type of conveyor application the switch shows no sign of damage and the contacts show continuity i was wondering if it were possible that there is a flaw in the motor manufacture either with the bearing or the windings or perhaps if incomplete engagement of the switch when used frequently by store personnel were creating a low voltage condition i checked the incoming power and it is within the nameplate range
RE: motor failure with locked rotor
There are of course numerous possible causes of bearing failure. Disassembly/inspection might cause some clues. Some items that come to mind:
- The gearbox is imposing excessive radial loading on the motor bearings.
- contamination of the bearings by the environment
- improper greasing of the bearings - overgrease, incompatible grease, etc
- severe operation causes high temperatures which cause all the grease to run out of the bearing.
RE: motor failure with locked rotor
RE: motor failure with locked rotor
If the windings are not burned I would suspect a bearing failure.
Can the motor be banged around in any way to put it out of alignment? Could it be hit by personnel or objects?
Make sure personnel are FULLY engaging the drum switch!
Have you confirmed the voltage AT the motor leads, WHILE she is LOADED?
Does the motor come with a manual overload?
RE: motor failure with locked rotor
Street level- is it outdoors? TEFC does not necessarily mean the motor is suitable for outdoor use... It needs suitable degreee of ingress protection, something like IP55 or better to make sure the bearings are suitably protected from the environment.
RE: motor failure with locked rotor
RE: motor failure with locked rotor
Disassembly of the motor would be most revealing as to what happened. I suspect you will find either just the run or start windings burned and have melted the insulation so as to lock up the rotor!
Before you replace the drum switch (replace it with one that is twice the HP capable), do a conveyor load test. Load it up and stop it repeatedly and confirm that it can start the conveyor under those conditions each time!
A motor with a manual overload is what I suggest. This of course means running a line leg through the overload first and then back to the switch.
RE: motor failure with locked rotor
RE: motor failure with locked rotor
From the information of the previous posts it seems that your motor is failing due to siezed bearing/bearings.
In some cases motors can burn up and some wire strands gets caught on the rotor cage fins causing locking.If this was the case,the bearings would not necessarily be faulty.
I don't think you have mention that anywhere.
There is a possibility (albeit remote) for C flange motors to fail with drive end bearing siezed.It happens because of a lot of slop (looseness)on spigots causing motor to be badly misaligned when it is bolted down.This misalignment
can be severe enough to preload the DriveEnd bearing to destruction.
We have to rebuild spigots on large Generator Armatures for that same reason.After a few assemblies and disassemblies,spigots can get fairly sloppy.Your motor most likely has a shaft Spline that inserts in the Gearbox.They will not tolerate too much misalignment.
GusD
RE: motor failure with locked rotor
Smaller motors I have seen have a slot liners and top stick that look like plastic... and when the motor is overloaded, they sure do MELT like plastic. ;)
RE: motor failure with locked rotor
RE: motor failure with locked rotor
RE: motor failure with locked rotor
RE: motor failure with locked rotor
i have had two failures with single phase capacitor start motors connected to a conveyor. the motor is wired 22o volt through a drum reversing switch. in both failures the rotor was locked
///This can be of a mechanical origin or electrical origin.\\\
when the motor was disconnected from the gear reducer. the reducer and drive chain spin free when the motor is not connected.
///The conveyor still may be the culprit as well as the motor mechanical internals.\\\
when new motor is installed machine runs normally and amperage reading is below full amp rating. is the failure due to end user overloading conveyor or is there another electrical cause such as reduction of voltage by power utility ?
///If the motor is sensitively protected (this has not been addressed yet) and the power quality is right, then the motor electrical portion will not show major symptoms, e.g. burned wiring, smell, etc. Even, if there is some wiring melt, it should not be catastrophical to lock the motor. If the motor is not sensitively protected, then the wiring melt may cause the motor to be locked.
The mechanical failures have been addressed in the above postings. The single phase motor may have a centrifugal switch that might disintegrate and potentially lock the motor. Also, the rotor cage might experience mechanical malfunction that may lock the rotor.\\\
RE: motor failure with locked rotor
RE: motor failure with locked rotor
RE: motor failure with locked rotor
Conveyorman should cajole (hey, we're from NYC!)the motor manufacturer to disassemble the end-bells and check the bearings, if the rotor moves freely so much for my overheating theory. If not then saw the motor in half lengthwise and see where the rotor failed.
Here's a thought that just occurred to me- is any type of crud getting sucked into the external cooling fan housing and jamming the rotor?