Jethro wrote:
I did a stupid thing - but I am curious.

Someone lent me his air compressor on which he had a 3-prong male
plug. He had clipped off the ground, leaving the other two. I
carelessly plugged the thing into a wall receptacle without paying any
attention. That's the stupid part.

I turned my back on the receptacle to flip the compressor on switch
on.
I heard a strange sound, turned around, and a little black smoke was
coming out of the receptacle where I had plugged the male plug in.
Needless to say, I immediately removed the plug. When I did, one
metal prong pulled out of the plug remaining in the receptacle. I
turned the circuit breaker off and removed the prong.

I think I must have plugged the thing in backwards, since the ground
was missing on the plug to prevent that. Dumb! Anyway, I now am
curious as to why the goof did not trip the 15A breaker. I think it
should have. Maybe the breaker is bad?

Agree?

I will replace the compressor plug of course.

Thanks

Jethro

Breakers take a finite length of time to trip, and whatever burned
apparently limited the current quickly enough to keep the breaker from
burning but still kept the heat going. Not too unusual, really.

Your plugging it in "backwards" could (NOT did!) possibly have been the
reason, and also why it didn't draw enough current to trip the breaker. I
say that while assuming that the compressor was sitting on a cement floor or
somehow in contact with other earthed surface/s. IF THAT'S THE CASE, THIS
IS A VERY, VERY DANGEROUS EQUIPMENT!!!! IF this is the case, there is a
serious fault with the unit.

Cutting off the ground prong is also the height of stupidity, especially for
something meant to be used where an air compressor is! That thing could
easily kill someone!! Either get a ground put on that unit, or don't plug
it in!
I have to wonder if tripping a breaker might not be why the owner ripped
it out. It's common to want to plug these things into a two prong outlet,
but very stupid if a converter isn't used to provide a working ground for
it. The plug converters cost less than a $ for cryin gout loud!