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maximum temperature on a bearing on electrical motor

maximum temperature on a bearing on electrical motor

I have a 3.5 MW motor, syncronous, with two sleeve bearings, (zoelern manufacturer) and i have temperatures up to 93 º C, and the manufacturer of the motor, says me that i could put the alarm temperature on 95ºC and the stop on 100 º C, this seems to be too high, does somebody knows about some standard that talks about this, cause i´ll like to have something like an standard for discussion.

RE: maximum temperature on a bearing on electrical motor

It does seem a bit high for oil sleeve bearings but the manufacturer is the one who dictates the trip and alarm settings. Many NEMA motors have similar bearing temperature  ratings but there is variations among manufacturers.
If it has auxiliary cooling, then maybe the values are correct.

RE: maximum temperature on a bearing on electrical motor

95 deg C for white bearings is normally the trip level. Normal alarm I have seen is 80 deg C and 90 deg C as trip.

Is this a new development or does this motor have a history of such high temps ?

Even if the manufacturer says 95 deg C is the alarm, 93 deg C is too close for comfort.

RE: maximum temperature on a bearing on electrical motor

I've never come across an actual standard. There are so many variables: ambient temp, type of lubrication (pressure or oil ring), type of lubricant, speed of motor etc. One rule of thumb that I have come across quite a bit is called the 80, 90, 100 rule. 80 deg C is normal, 90 deg C alarm and 100 deg C trip. I agree with edison123, it sure seems that your running too hot.

RE: maximum temperature on a bearing on electrical motor

To OP.

What is the temperature you are measuring, the oil or the white metal ?

RE: maximum temperature on a bearing on electrical motor

one of the items you have to remember is there is a time factor..  Frequently when there is a problem,  you are not dealing with a steady state situation;  the cause of the heat generation maybe somewhat localised,  and not located in close proximity to the sensor,  or if the oil temperature is being measured,  there's a heat sink effect depending on the volume of oil.  For these reasons,  and depending on the set up,  it is prudent to keep the alarm and trip settings at conservative levels.  They are there to alert you to a situation,  and prevent consequential damage.  To hot can be too late !

RE: maximum temperature on a bearing on electrical motor


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