How to reduce big motor tripping problem in high temperature environment

[ws0619]

Hi,
To rise the oven temperature, I try to increase my oven blower motor HP from 7.5HP to 10HP then to 15HP. The result is I have achieved my objective, the oven temperature rise when I increase the motor HP.However, those induction motors cannot run more than half year. The major problem is motor bearing broken.
May I know how to solve this problem?
Is it due to too high environment temperature,causing motor to trip?about 70-80degreeC (heat transfer from oven). I can't find any solution for it.
Please enlighten me.
Thanks!

 

[jim hardy]

you're failing bearings?

sounds like a lubrication problem to me.

perhaps a mechanical or petroleum engineer in the house?

Have you looked into Dupont Krytox high temperature grease?

 

[Yuri B.]

If it would not require hundreds meters of ducts put the fan outside the shop.

 

[ws0619]

thanks for your idea.Now i am looking on the lubricant melting temperature. Most of the motors have bearing problem initially then develop into winding short-circuited problem.

 

[BhutJolokia]

I have a bit of experience with motors (I am constantly dealing with 250 lb fan motors and a few blower motors.)

Anyway, I think the problem lies in the grease in your bearings overheating (as you have raised the amount of heat that they have to tolerate by a good amount) leading to the grease leaking out, causing your bearings to eventually fail when enough grease has leaked out.

When you say the bearings fail, what specifically do you mean? If you could post a picture of what these bearings look like once they have failed I am sure I could diagnose the problem.

With that said, when I have bearing issues it is always due to low grease. During the summer months when it gets up to 90-100 degrees here (on top of the high heat these motors already produce) I have to regrease the bearings very frequently. Well, very frequently as in once or twice a month as opposed to once ever couple of months during the winter.

Also, as you have doubled the horse power that these motors are putting out I would also suggest that maybe the bearings are not able to handle the increase and you may need to look into a higher grade of bearings, or have someone machine you a set at a stronger grade than the ones that you're currently using.

Really, it's hard for me to guess without seeing how the bearings look, or hearing how they sound before they go out. Hope this helps!

 

[jim hardy]

you say you're failing windings too?

are these fixed speed induction motors, or perhaps equipped with variable frquency drives?

put a thermometer on motor case near where cooling air comes out. Compare to motor datasheet...

 

[ws0619]

I have sent most of the motors for rewinding, asking the technician to take the photos on the broken bearing part.
I plan to reduce the environment temperature,maybe is because of high environment temperature, causing motors easily to trip.
Fixed speed induction motor, direct connect the motor to starter, no use of any inverter.

 

[ws0619]

Attached with the bearing fail photos.It is actually fail on the load side bearing, but the bearing that located near to cooling fan of induction motor, it is in good condition.

Hope you all can enlighten me on how to cure bearing failing problem.

Thanks!

 

[jim hardy]

i look forward to a bearing expert's observation.

Can you cut or break the bearing race and show the actual curved groove where the balls roll?

That helps the "bearing doctor" diagnose.