Re: Earth leakage and SS Variac

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

Original poster: "Metlicka Marc by way of Terry Fritz <twftesla-at-qwest-dot-net>" <mystuffs-at-orwell-dot-net>



Tesla list wrote:
> 
> Original poster: "Byron by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<byron-at-4zzzfm-dot-org.au>
> 
> On Sat, 1 Sep 2001, Tesla list wrote:
> 
> Up to now, prior to starting ti play with NSTs and ignision coils, I
> normaly play with low voltage stuff.
> However, due to my ability to make stupid mistakes while running things
> and being a little clumsy, I'm trying to put in a few more safty levels
> than normal. I know they aren't garenteed to work, but circuit breakers
> and earth leakage will add a little more, if they save me once, it's good
> enough for me. :)

Byron,
I think the use of contactors with interlocks and lockouts for control
voltages is the best bet. If control voltage is dropped out then we know
a contact cannot come in, just remember that contacts stick or fuse
together, so the choice of "power on" indicators is the blessings here.
I like the timer i have in my control that brings the main in after the
gap fan comes to speed also, Everyone knows that when they here the fan
coming up, back up (well at least ten feet??). I've even hit the on
button while within the "no fly zone" and either made the hasty retreat
to safety or hit the off button to drop control power again.
a breakdown of my control circuit can be found at:
http://www.fortunecity-dot-com/meltingpot/syria/1210/id34.htm
maybe some of it can be useful?

As far as the solid state variac goes, David sharp has a very promising
design in the works. Looks good, smells good, so it must taste good? we
shall see (hurry up david!)
>From what you're suggesting, I think you could build industrial control
cabinets because that's basically it. If the contacts can't come in,
they won't, so use mechanical as well as electrical interlocks, use
double the relays to direct control power, interlocked of coarse. I like
flashing "green is good" lights for all safe and above all have the
little "I and only I operate this system" speech before firing among
friends.
Take care,
Marc M.