Re: control panel

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Gregory Peters by way of Terry Fritz <twftesla-at-qwest-dot-net>" <s371034-at-student.uq.edu.au>



> 1.  Fuses (or heavy duty circuit breakers) for input power. 


I would NEVER rely solely on circuit breakers for a large coil. 
Circuit breakers are prone to not tripping reliably. I have a 32A 
breaker in my box that easily holds off 50A for over a minute. Also, 
circuit breakers can weld shut. 

I DO have breakers in my cabinet, but these are also protected by a 
fuse. The system is designed to trip the breakers under a "normal" 
fault (me just removing a bit too much ballast inductance), but a 
large sudden unexpected fault (say a short in the ballast) will trip 
the fuses ~instanty. I have the breakers set at what the wires can 
handle continuously. The fuses are set at nearly twice this rating. 
This way I should bever blow a fuse unless something really goes 
wrong and the breakers don't trip first. But the fuses offer that 
final bit of protection.

Use good quality HRC (high rupture capacity) fuses. These use a 
silver wire in a silica powder. When they trigger, the silica powder 
makes arcing almost impossible. Some other types of fuses can arc 
across if the current is high enough (kind of like a welding arc - 
the wire melts at one end, a small arc forms and spreads across the 
fuse when the rest of the wire melts). 

It is quite scary how fast the house wiring heats up with a dead 
short :)



Cheers,

Greg.