Due to having found a 7.5 HP single phase motor, I swapped the three
phase motor on my compressor for a single phase Marathon motor:

http://igor.chudov.com/projects/Quin...e-Phase-Motor/

What surprised me was that this 7.5 HP motor has insulation class F
and, apparently, it would be normal to see a rise in temperature to
311 degrees F during continuous operation, at maximum ambient
temperature of 105 degrees F. We rarely get 105 degrees around here,
but 100 is normal for a summer, so the motor can get to way above the
water's boiling temperature.

This seems hazardous to me, personally.

I did verify that the amp draw of this motor, with the compressor
close to full pressure of 140 PSI, is about 30 amp, so the motor is
functioning within its 30 amp nameplate amp draw.
i

Ignoramus21117 wrote:

Due to having found a 7.5 HP single phase motor, I swapped the three
phase motor on my compressor for a single phase Marathon motor:

http://igor.chudov.com/projects/Quin...e-Phase-Motor/

What surprised me was that this 7.5 HP motor has insulation class F
and, apparently, it would be normal to see a rise in temperature to
311 degrees F during continuous operation, at maximum ambient
temperature of 105 degrees F. We rarely get 105 degrees around here,
but 100 is normal for a summer, so the motor can get to way above the
water's boiling temperature.

This seems hazardous to me, personally.

I did verify that the amp draw of this motor, with the compressor
close to full pressure of 140 PSI, is about 30 amp, so the motor is
functioning within its 30 amp nameplate amp draw.
i

Ought to be good for driving moisture out of the windings. I'd certainly
consider it to be hazardous to not have at least a "Caution hot surface"
label on it, or better yet a wire guard around it.

The INSULATION is rated at 311F but that is the temp for the most inner
part of the coils inside the motor. The outside case would have to be
much less than that to get any thermal heat transfer

Ignoramus21117 wrote:
Due to having found a 7.5 HP single phase motor, I swapped the three
phase motor on my compressor for a single phase Marathon motor:

http://igor.chudov.com/projects/Quin...e-Phase-Motor/

What surprised me was that this 7.5 HP motor has insulation class F
and, apparently, it would be normal to see a rise in temperature to
311 degrees F during continuous operation, at maximum ambient
temperature of 105 degrees F. We rarely get 105 degrees around here,
but 100 is normal for a summer, so the motor can get to way above the
water's boiling temperature.

This seems hazardous to me, personally.

I did verify that the amp draw of this motor, with the compressor
close to full pressure of 140 PSI, is about 30 amp, so the motor is
functioning within its 30 amp nameplate amp draw.
i

On Thu, 25 Jun 2009 23:24:14 -0500, Ignoramus21117
wrote:



What surprised me was that this 7.5 HP motor has insulation class F
and, apparently, it would be normal to see a rise in temperature to
311 degrees F during continuous operation,


The label only indicates that it has class F insulation. It doesn't indicate
the design temperature rise. Class F insulation with class B temperature rise
has been fairly standard for more than 30 years.

A motor that didn't have at least class F rated insulation would not be worth
manufacturing these days.


Mark Rand
RTFM

Ignoramus21117 wrote:
Due to having found a 7.5 HP single phase motor, I swapped the three
phase motor on my compressor for a single phase Marathon motor:

http://igor.chudov.com/projects/Quin...e-Phase-Motor/

What surprised me was that this 7.5 HP motor has insulation class F

and, apparently, it would be normal to see a rise in temperature to
311 degrees F during continuous operation, at maximum ambient

FAIL