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G'day DBN & Mike.
The temperatures you have recorded do not seem unduely high. You need
to remember that the insulation is most likely rated for 90 degC.
(161 degF) temperture rise, this is typical of modern electrical
materials.
First question. Does the motor pass the smell test? There may be a
sweet oily solvent smell, thats normal, but an acidic or acrid smell
indicates trouble.
Question 2: Do the terminals get hotter than the rating of the
connecting cable insulation? The connecting cables with PVC
insulation generally have a temperature rating of at least 75 deg.C.
After extended running and with the motor disconnected at the wall
outlet, measure the terminal temperature (you can get temperature
marker crayons but a finger will do). Note, higher temperature rated
cables are often used for machinery wiring, often rated to 110 deg.C;
this grade of wire is used in fluorescent luminaires.

The only reliable winding temperature measurement is to measure the
winding resistances when cold and hot and compute the temperature
difference. Handbook type advice would generally assume this means of
measurement.

I would suggest that if the motor does not smell bad, the terminal
temperature is less then the connecting cables insulation temperature
limits and the surface temperature of the motor case does not create
a fire hazard then all is well.

Always keep flammable materials, dusts and fluff away from the motor
and ensure the air flow is unrestricted. Then if the motor does give
up you only have to replace the motor not your house. This is good
advice for any electrical equipment!!

One good turn deserves another
Regards,
Ian


--- In 7x12minilathe@..., Druid Noibn <druid_noibn@...>
wrote:

Hi Mike,

I have a handbook and will look at it later.

I would gather it has more to do with the classification of the

motor. I've worked on a few motors and drive systems over the last
40 years or so and these run a tad hot. Of course, they "might" be
rated as such. Also, as noted, they typically run for short
durations.

The data were posted for all to have.

Thanks!

Take care,
DBN

Michael Taglieri <miket--nyc@...> wrote:
My copy isn't handy so I can't confirm this, but I think

there's a

section on electric motors and their acceptable temperature rise in
Machinery's Handbook.

Mike Taglieri miket--nyc@...

The belts were removed but the

stock pulley was left on. The motor had unobstructed airflow and
should be considered "new." The ambient temp was 61.2F (16.2C).

05 min. – 12.1F (6.7C) rise
10 min. – 25.0F (13.9C)
15 min. – 35.6F (19.8C)
20 min. – 42.4F (23.6C)
30 min. – 53.0F (29.4C)
40 min. – 58.9F (32.7C)
50 min. – 62.2F (34.6C)
60 min. – 64.3F (35.7C)

The probe was located on the upper part of the

motor

housing, between the motor body and the junction box.

Without noting all of the readings, in the course of:
13 minutes – temp rise 39.3F;
30 minutes – 49.7F;
46 minutes – 58.1F;
63 minutes – 63F – shut-down motor
66 minutes – 65.7F