Does anyone have a publication no. or link to the IEEE formula for calculating maximum allowable temperature rise for installed electrical components?

Kurt,

For electrical insulation systems it is IEEE Std 1, which has just been re-voted and re-issued.

Which other components are you interested in?

Howard

Mr.Penrose-Great Pleasure to hear from you,Iam a follower of your web-site,Iwas looking for information regarding a 175 watt120v/24v Control Transformer.Currently operating at 63.3deg.C surrounding area is at 43.3deg.C a20.1 deg.C rise.The transformer is loaded at 4.9Amps and is confined by wireways and other cabinet components.Iam proposing relocating within the cabinet to a more open area,but did not know what a normal temperature for this transformer might be.I would also be interested in hearing from you more about creating a baseline for a infrared motor maintenance route.As you know it is often impossible to capture both end bearings and most problems would probably arise in these areas as oposed to the casing,any suggestions?I look forward to someday taking your Motor Signature Analysis course,till then I am motivated to put our new P-65 Flir to as many uses as possible,Thank You,for your reply Sir.

Kurt:

Thank you.

The standards that cover testing for a control transformer are IEEE 388 and IEEE 389. I do not remember, however, if they cover temperature.

The IEEE Std 1 does cover it, however, as the rating is still a limit of the insulation class of the transformer. On average, they will be rated at 25C or 40C ambient (surrounding temperature) with the upper limit being about 10C below the insulation class temperature. The allowable rise is the difference between the actual ambient and the actual temperature.

Insulation Class Limits:

A = 105C
B = 130C
F = 155C
H = 180C
N = 200C

for instance, if the transformer is rated 25C ambient with a class F insulation system:

Under full load, the maximum surrounding temperature for proper cooling should be 25C;

The maximum rise should be 155-25-10 = 120C

With a maximum total temperature of 145C.

Now, with the bearing and electrical testing. I have placed a copy of the old Infraspection Institute standard on electrical testing at http://www.motordiagnostics.com/presentations.htm (sorry, too large for this forum) in Adobe Acrobat for free download.

Bearing temperature, for ball bearings, should be the same as the bearing housing temperature. The max temp should be based upon the type of lubrication (organic or synthetic).

The attached presentation provides those temperatures on slides 15 and 16 (Adobe Acrobat) - from my presentation at IMC-2005.

Hope that this was helpful. Look forward to seeing you at one of my classes in the future.

Howard

Bearing_Greasing.pdf (823 Kb, 53 downloads)