Re: DC power on Tesla secondary (was 20 joules at 100 bps vs 4 joules at 500 ...

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: FIFTYGUY@xxxxxxx 

In a message dated 8/14/05 2:48:18 PM Eastern Daylight Time, 
tesla@xxxxxxxxxx writes:
>A Gerret +P 44 caliber magnum round (about the max any normal human
>would fire from a hand gun) is about 2000 joules.


    In American terms, that's about 1500 ft-lbs. BTW, that's a darn 
hot load for a .44 Remington Magnum cartridge. And yes, about the 
most oomph "normal" folks tolerate from a handgun (especially the 
*Garrett* +P ammo with increased chamber pressure, extra powder 
loads, and heavy bullets).



I hope this is not too off-topic, but is that kinetic energy of the
bullet? chemical energy in the propellant? or what?


    Kinetic energy of the projectile (specified typically at a 
distance not far after it's left the muzzle). Only about 35% of the 
chemical energy available from the powder is transformed into 
translational kinetic energy of the projectile. Interestingly, this 
about the same effciency as a typical internal combustion automobile.


The biggest bang I ever got (apart from that time I snipped through a
live 240v extension cord with wire cutters)

    Heck of a thing to do to a nice pair of cutters...


Larger coils, like industrial motor drives and traction inverters,
can have rupture energies comparable to the rounds of ammunition
Terry was talking about. But I've never seen an electronic engineer
working on one live with a flak jacket! I guess they are designed
_not_ to launch sharp pieces of metal at supersonic velocities.

    I've seen motor drives experience explosive catastrophic 
failure. Most of the time the largest pieces of metal are the 
heatsink(s), which are usually bolted into a panel or support 
structure at the rear. Thus any blast just blows loosely mounted 
pieces of plastic, bits of wire, and circuit boards off the front of 
the drive. These fragments don't have much long-range penetrating 
power due to their irregular shape and low density.
    Because of air pass-through for cooling the drive, the blast 
from a power semiconductor or big circuit trace vaporizing is vented 
into a relatively large space before it is somewhat shielded by a 
cover (in non-chassis mounts). The cover would also act as a shield 
before it was blown off. Perhaps more importantly, any cover helps to 
arrest the large ball of flame or plasma...
    Put that same power semiconductor inside a closed chamber (a gun 
barrel?) and you could surely use its explosion to propel a proper 
metal projectile.
    Don't forget about current ratings in power distribution and 
components - let a fault current exceed the "explosion current" in a 
piece of equipment and it will do just that. So yes, technicians 
sometimes work on live equipment wearing "flak jackets" to protect 
from "arc flash".

-Phil LaBudde