Electric Motor & Bearing

Because of Heat generated in a electrical motor,the bearings in the input / output ends failed (ie grease inside bearings have come out as a liquid), and leads to failure of systm later on.

Any one can help to know the temperature limit for the bearing usage, since most of the bearings doesn't mention out temperature. Normally talkes about hrs of running, load Etc.,

Thanks and Best Wishes

Mani VS

Reply to
mvsmani
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Hi Mani, This is not a simple question, but most bearing manufacturers have applications information that can help you, for example, see

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the end is the engineering data which will allow you to calculate life cycle based on many factors, including lubrication and temperature.

Reply to
Jeff Lowe

Bearing manufacturers typically publish a LOT of technical info about their products. Try Koyo, NSK, Timken, etc., and look carefully through the data they offer.

Then, consider that the operating temps for the bearings might not matter as much as just switching to high-temp grease that'll stay inside the bearings and do its job.

KG

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Reply to
Kirk Gordon

It's not easy to figure out which one came first: grease overheating leading to bearing failure or bearing seizure leading to an overheating which liquefies the grease. Keep the the second hypothesis as possible too. Thermally induced preloading can seize bearings pretty quickly. Good luck and check the references that the others have suggested too. Watch for thermal mismatch of shaft and housing versus the bearing race material (normally AISI 52100 I think).

Gilles

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Reply to
Carrier

It is an engineering problem involving class of bearing fit on mount and shaft, ambient operating temperature, materials used, efficiency of bearing and coupling, actual voltage and motor voltage type and motor class and frame, number of starts and stops, and a few other considerations.

Experienced engineers usually do not calculate each and every one in a design, but rather adjust one or two parameters if one of them in the design falls outside the manufacturers suggested parameters. >the bearings in the

IMHE, there are three killers for bearings

-- striking/damaging a bearing during handling or installation,

-- undersizing the other axis, and

-- overpacking the bearing with grease and creating ploughing which heats the bearing grease through shearing and causes it to flow out of the race. (often done by maintenance procedures which call for two shots in the zirk monthly as if the bearing is a steel-on-steel farm implement shaft)

yours sounds like you may have missed the one-third full rule or somebody pumping it full by using the zirk scheduled

If the bearing unloaded ambient is within limits, and the couplings and shaft are within runout limits, and you haven't undersized your wiring from too long a run or too small a wire or cheap rubber tape (cheap chinese thermally insulating motor tape rather than 3m thermally conducting) and you have been filling only the bearing lower third with grease if dry before installing, and you have been using ball and roller bearing grease rather than "the stuff in the can", then you could look to a higher temperature roller bearing grease.

Reply to
Hobdbcgv

Hi All,

I would like to thank all & Jeff, KG, Gilles, TOM and Hobdbcgv for the contributions made and the light thrown on the subject to understand this better.

One of the reason what we have considered was " the ventilation provided for the electric motor for cooling is not sufficient". Which makes the motor to overheat and since the heat generated is not dissipated it makes the components to overheat and damage.

request you all the send your views about the ventilation and amount of air circulation needed to cool the motor, heated during running and any other techniques to dissipate the heat

We elliminated the overpacked grease phenomenon, since it is a self lubricated bearing. But it is quite interesting to know about how the over packed grease could reduce the life of bearing.

The thermal mismatch also provided me to get more details about the materials of construction.

Thanks to every one of you for your contributions Thanks and Best Wishes

Reply to
mvsmani

Motor manufacturers will give a running temperature.. often as ambient + 70 C for their motors.

Where overheating may be a problem I stick temperature labels which have patches which darken when heated to a temperature to the case, and then inspect them after the motor has been run.

One manufacturer of these labels ( the one I use ) has a sight at

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Series 8 Range B covers 77 C to 116 C in 8 steps, and is normally the one I need to use.

Hope this helps

Reply to
Jonathan Barnes

Mani VS,

I was told once by a electric motor designer that there was no such thing as an electric motor that was too cooled!

Jonathan's suggestion will certainly get you something to work with as far as the housing temperature. Bearings seize often when the shaft is too hot and reduce the built-in play between the inner race and the outer race. The best thing you can do is to try to measure the shaft temperature near the bearing inner race. And this can only be done by using a IR pyrometer or some other non-contacting instrument. Once you know the shaft temperature, you can adjust the race-shaft interference to the recommended running values - it's in the order of

0.0000-0.0002"or something in this range.

Good luck!

Gilles

J>>One of the reason what we have considered was " the ventilation

Reply to
Carrier

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