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A $20 mistake - and a good lesson!

I run a phase converter in my shop. The other day I flipped on a

3-phase machine and it just buzzed. Without thinking much, I just flipped it off and back on again - it started normally. I was working along and suddenly I happened to look at the machine's power cord. The plug was smoking heavily and one of the lugs was just about to melt. It wasn't a short, just an almost-open dropping 240VAC across a significant resistance. Today I went up and ponied up $20 for a new 3-phase plug (ouch!) and I promise myself if I ever hear a machine just buzz when it should spin right up, I'm going to tear down the wiring right then and not wait for the smoke to come out.

Grant

Reply to
Grant Erwin
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Grant Erwin scribed in :

this is one of the biggest causes of house fires, the partial connection to a heavy load. it starts to arc. heard about arc welding? it melts metals you know (-:

I've got my family almost trained now. any buzzing or crackling in a power socket/extension etc, and they put it off and call me. mostly.

swarf, steam and wind

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Reply to
DejaVU

Deja sez: "... it starts to arc. heard about arc welding? it melts metals you know (-: ..."

Grant was describing resistance heating, not arcing. Take a look at your electric range; that is resistance heating, not arcing. Simply put, an arc is a form of resistance heating where the air contributes the "resistance".

Reply to
Bob Swinney

Mmmm. Not so much the air, but the plama inside the arc.

Nitpic nitpic nitpick....

Jim

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Reply to
jim rozen

Jim sez: "Mmmm. Not so much the air, but the plama inside the arc."

Not to be nitpicky, Jim, but can you 'splain me more about this here *plama*

Bob S.

"resistance".

Reply to
Bob Swinney

in computer room raised floor installations, folks have learned to moniter the temperature of service panels and underfloor connectors, part of a decent "facility managment" team these days.

years ago, _everything_ was hardwired, so the connections were _not_ under the floor. the reason those commercial hi-amp connectors cost like gold is the fire-rating design and (likely) product insurance.

--Loren

Reply to
Loren Coe

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