Electric Motor Bearing Heaters 1

[jdogg05]

I understand for storage and preservation a lot of larger electric motors have bearing heaters to keep the bearings in a certain termperature range in cold climate conditions. What exactly is the rationale behind this? I understand why shafts need to be rotated to avoid brinneling, but why do the bearings need to be kept warm? I heard it has to do with the freeze/thaw/freeze cycle that happens in cold climates. But why does this matter? Does the lubricant degrade? Does moisture somehow get in from the outside?

 

[itsmoked]

jdogg05; I'm only confirming why there might be bearing heaters required by some motor suppliers.

I also fully agree with Bill's point that if there are stator/armature/winding heaters they will certainly cover the bearing aspect too. It only needs a few degrees to block condensation caused by a shifting ambient/dew point.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[SceneryDriver]

Is there any merit to the idea that bearing heaters might be used in extremely cold climates/conditions to ensure proper clearances are maintained between rolling elements? Can a roller/ball bearing that has proper clearances at room temp (70F) be damaged by trying to run it at -50F? Can running a bearing at arctic temps cause damage from cold embridlement?

For reference, I work in the entertainment industry; not much chance of us seeing -50F in most theaters.


SceneryDriver

 

[squeeky]

We are in Africa but condensation is a problem. Our motor supplier has internal anti-condensation heaters in all motors over 22kW as standard. These are wired to the normally closed of the motor contactor so they come on when the motor stops. In storage they are also connected.

In cold climates any residual moisture will freeze and expand. It moisture can be drawn into the motor when it cools. Rust and expansion would be the two main issues. For the rust, you can also insert schattes of VPI (Vapour phase inhibitions). You can do a Google search for VPI or VPCI (Vapour phase corrosion inhibitions). If you need more please let me know.