Effects of the magnetizing of non-magnetic radial bearings?

[bryjarmoc]

We build electromechanical motors (ac & dc). We are having an issue with bearings in a particular motor drawing "high amps" during testing. We have traced the issue down to the change in bearings. One of the questions that has been raised is "Could the bearings have been magnetized? If so, what are the affects of the magnetizing of the bearing"

Any help or info would be greatly appreciated.

Thanks

 

[sreid]

Although magnetized bearing are not considered a good thing,I doubt that this is the source of your problem. If there is a current path though the bearing, that absolutely needs to be corrected.

 

[bryjarmoc]

I guess a more specific question would be, Can magnetizing a "non-magnetic" bearing cause resistance in the bearing movement? (theory being that the "drag" inside the bearing is causing the high amps in motor).

 

[sreid]

Clearly a magnetized bearing will have additional drag. For extremely small bearings/motor, this might be significant. For larger motors (say 1/4 HP and up), I don't think that the additional drag would be significant.

Are the bearings magnetized? How does the drag "Feel" compared to an unmagnetized bearing.

 

[dimjim]

High starting torque may be a result
of hi preload in the bearing or micro
welding by a current passing thru the
bearing.

 

[0818758045]

When the bearing is magnetized, it will magnetize all metalic partical into it. That causes the damage the bearing. On the drage force, I don't think will be the problem since it still is rotatable. Bearing is magnetized normally when it is heated by eddy current heater, and has to be demagnetized when temp. reached the needed level.

Verapan
NSK bearings Thailand
Motion and Control

 

[0818758045]

One more thing is that if the motor draws high amp,issues to be considered are
1. Bearing magnetized and stall caused by induction current
2. Current go ground through the bearing

Both problem can be prevented by using insulated bearing.
Please check the bearing condition after use, to see the electric pass.So I could know some more detail of the problems.

Thank you
Verapan
NSK bearings Thailand
Motion&Control