Exploding MV motor weatherheads?
Exploding MV motor weatherheads?
(OP)
I have seen ground faults inside junction boxes at MV motors do a good deal of damage to the enclosures.(There have even been reports of fatal injuries to people near the motors when such happens.) Lots of "arc" damage will be present but not with my newest MV fun! In the most recent incident some sort of fault occcured inside of the motor (2300v, 300HP, 4pole)that caused a cast iron weather head to fragnment into about 10 pieces with enough velocity to put 1/4" dents into a sheet meatal building about 20 ft away. No arc damage visible to anything in weather head. No blown fuses or GF tripps. Motor meggs good so I am guessing some kind of phase to phase fault but the cast weather head exploding seems odd to me and would like any feedback others may have on this matter. Thanks.





RE: Exploding MV motor weatherheads?
The old "opposites attract" and "likes oppose" can really put a hurting on anything nearby. :)
Ever see a welding cables slap together? Or hear wires "ringing" in a conduit during a dead short? The magnetic pulse going through the wires cause them to vibrate (that's too light of a word for it) violently.
RE: Exploding MV motor weatherheads?
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RE: Exploding MV motor weatherheads?
Another thought, if you have a good protection scheme working properly (you could test it...) and didn't trip, then one has to wonder if there is can be some cause that does not involve electrical fault. Cast iron can be a brittle material. Perhaps bolting configuration was putting it in stress? Unusual thermal stresses?
It's a headscratcher.
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RE: Exploding MV motor weatherheads?
RE: Exploding MV motor weatherheads?
RE: Exploding MV motor weatherheads?
A combination of moisture and insulation leakage current may have produced enough Brown's Gas to do the damage you describe, and not leave much trace other than the damage. I once had my car battery blow the top off from a Brown's Gas explosion and I have cleaned up after a number of other such explosions. A small volume of Brown's Gas will do a lot of damage and the product of combustion is water vapor.
(I no longer spec, install or connect battery chargers on standby diesel sets. There is too much drama when the battery explodes.)
Bill
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"Why not the best?"
Jimmy Carter
RE: Exploding MV motor weatherheads?
Not wrapping properly is a little like using duct tape to fix a leak in a garden hose. It might work for a while but eventually you're going to get wet.