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gaux (Mechanical)
7 May 09 13:59
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.
thanks
lansford (Electrical)
8 May 09 4:07
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.
JIM
 
edison123 (Electrical)
8 May 09 8:28
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.
starkopete (Electrical)
8 May 09 11:37
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.
starkopete (Electrical)
8 May 09 15:09
For what it's worth, I found this in my files. It's from Renk (another bearing manufacturer).  
edison123 (Electrical)
8 May 09 21:54
To OP.

What is the temperature you are measuring, the oil or the white metal ?
macmil (Mechanical)
9 May 09 13:58
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 !
gaux (Mechanical)
10 May 09 18:50
thanks...
 

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