Below is a link to a webpage that describes insulation and how to figure the
maximum temperature. In your case, your reading 190 deg F (87.7 deg C) on the
outside of the fan motor. Where it counts more is at the mean turn in the
winding or it's middle deep inside. You can be assured it's higher there and
the wire temperature is what we worry about, or its insulation along with the
paper or plastic layer insulation is if it has any. In your case, I doubt it
has layers as most shaded coil motor coils are jumble wound on a plastic
bobbin. In the middle of this coil is the actual heat you have to worry about.
I'll about bet you can raise that temperature another 40 to 50 degrees F for a
total of say 230 deg F or 110 deg C. Now the motor should be designed to run in
an ambient temperature of 40 deg C (104 deg F) with a premissable temperature
rise according to the maximum temperature of the insulation class. You can see
this on the webpage listed below.
NEMA Insulation Classes;
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On 6/25/06 at 10:16 AM Ken wrote:
>I recently refurbished a dual 4-1000A RF deck. It came with a WW Grainger
>blower # 4C445.
>The blower is rated at 495CFM @0.0sp and 265CFM @.8"sp. The blower motor
>runs extremely hot.
>An infrared thermometer reads 190 deg. F on the motor after about 30
>minutes, and tops off at that. I haven't
>found any temperature rise specs. for these shaded pole motors, but that
>sounds excessive to me. Off the amp, with no
>back pressure, temp. is only 145 deg. F. The two SK-510 sockets provide
>little area for a blower this size.
>I have tried to make an adjustable vent, to relieve some of the back
>pressure, but with little temperature change, and I would
>rather not save the blower to lose the two 4-1000A's. Looking through
>Grainger's catalog, and looking at
>other amp blower usage, I have found their # 4C443, 70CFM @0.0"sp, 45CFM@
>.5"sp. Do you think this would be
>acceptable? I am only driving these 4-1000A's to 1,500w output.
>Thanks for your input,
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