Quantcast

Westy

the teste
Nov 22, 2002
56,231
22,264
Sleazattle
It's a 75hp electric motor that runs an ammonia compressor. Luckily the facility isn't 480v 3 phase, just 240v. The loose connection heated up all the insulation around the connection and cooked it all until it direct shorted!
Hard to tell if that hole is just from melted bits but it looks like it could be from an arc flash which is caused by the inductive load which is twice as high with 240v than it would be with 480, roughly speaking. Circuit breaker if sized properly would have prevented a meltdown in the case of a short circuit, but if it actually had an open circuit that motor becomes a generator and that energy has to find a path somewhere, it will basically create a lightning bolt that will seriously fuck shit up. Think of how an old points ignitions system works, you open the circuit to the coil and those angry pixies get seriously pissed looking for a place to go.
 

boostindoubles

Nacho Libre
Mar 16, 2004
8,521
7,120
Yakistan
Hard to tell if that hole is just from melted bits but it looks like it could be from an arc flash which is caused by the inductive load which is twice as high with 240v than it would be with 480, roughly speaking. Circuit breaker if sized properly would have prevented a meltdown in the case of a short circuit, but if it actually had an open circuit that motor becomes a generator and that energy has to find a path somewhere, it will basically create a lightning bolt that will seriously fuck shit up. Think of how an old points ignitions system works, you open the circuit to the coil and those angry pixies get seriously pissed looking for a place to go.
I think it heated up a bunch and got melty, then arced and blew the hole out. When I found the situation at 3am the engine room was filled with burned rubber smoke. Hadn't run that compressor in 2 years. The connection loosened up by itself inside there while it was off. Friggin industrial electricity is dangerous.
 

jdcamb

Tool Time!
Feb 17, 2002
20,061
8,792
Nowhere Man!
Once you go Melty shit gets fucked up. The indiscriminate nature of arcs determines the safe distance you need to be from them. Always. I don't trust myself to do that math. Avoid Melty...
 

sundaydoug

Monkey
Jun 8, 2009
682
359
Hard to tell if that hole is just from melted bits but it looks like it could be from an arc flash which is caused by the inductive load which is twice as high with 240v than it would be with 480, roughly speaking. Circuit breaker if sized properly would have prevented a meltdown in the case of a short circuit, but if it actually had an open circuit that motor becomes a generator and that energy has to find a path somewhere, it will basically create a lightning bolt that will seriously fuck shit up. Think of how an old points ignitions system works, you open the circuit to the coil and those angry pixies get seriously pissed looking for a place to go.
I wish I understood any of this. Sounds so cool.