Yahoo Answers is shutting down on May 4th, 2021 (Eastern Time) and beginning April 20th, 2021 (Eastern Time) the Yahoo Answers website will be in read-only mode. There will be no changes to other Yahoo properties or services, or your Yahoo account. You can find more information about the Yahoo Answers shutdown and how to download your data on this help page.
Trending News
Where does the explosive force come from an Arc Flash?
Yesterday a friend of mine turned a big refrigeration switch at work and it exploded. It had a three phase 480VAC power souce fused by three large 400A fuses and all three fuses opened. The door flew open with such force that when it hit his arm, his arm was opened up a foot in length down to the bone. The door continued flying open and hit an adjacent structure and left a huge dent in thick steel that the door was made of. No explosive gasses so how was the force generated to provide that much power. The electricity did not touch him and the switch is still in use this morning. What blew the door open?
1 Answer
- OldPilotLv 710 years agoFavorite Answer
The blown fuses are your clue. Some rare combination of conditions combined to create a need for a very high start current. This happens with refrigeration. My guess is that a compressor stopped at top dead center or some refrigerant liquid condensed in the compressor or a valve in the compressor stuck closed. Something like that. Your friend closed the switch, there was a locked rotor condition the 3 phase motor tried to start, could not and kept drawing more and more current trying to get enough torque to start, there was a very high surge====> the effect was a "lightening bolt" inside the box which did what you discribe.
Locked Rotor current runs 5 to 10 times normal current draw