Re: NST Protection Question [and story] + Australian Coilers?

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

Original poster: "Terry Fritz" <twftesla-at-uswest-dot-net>

Hi Simon,

At 12:57 PM 12/28/2000 -0500, you wrote:
>
>Hi all.
>I'm remaking my protection unit, to give it a bit more space, and to get
>rid of the power resistors in place of ceramic ones. 
>
>There's a bit of a story involved with one of my efforts to get the ceramic
>100W resistors required. On one of my visits to an electronics store, I
>asked the bloke [a young fellow] for the resistors, or information where to
>get them. He looked at me strangely, and went out the back. After some
>hushed conversation, an older bloke came out and said, "What in God's name
>do you want 100W resistors for?".. So I told him. He then proceeded to tell
>me how much power the resistors would drain, and told me it would be more
>efficient hooking up my younger brother to the coil instead :)

Don't hook your brother up!  Lots of juice in that circuit! :-)))

>
>Yes, there is a point to all of this. I started wondering; how much power
>is actually drained, and therefore, how much is performance dampened? The
>circuit is rated up to 15kV -at- 240mA, so if I am using a 30mA 15kV tranny,
>can I get away with smaller rated resistors?

I "try" to loose 5 to 10 percent of the coil's power in the protection
filter.  That is what all the models say is needed to provide good
protection for the tranny.  Since the coil's arc distance is proportional
to the square root of input power, that gives a 2.5 to 5 percent reduction
in arc length.  Of course, that is compared to the NST blowing which
results in an extended 100 percent reduction in arc length ;-)))  At the
bare minimum, safety gaps should ALWAYS be used.  I assume one will crank
the variac up a bit (or more) to make up for this.

>
>
>And finally, where the heck do I get them? [in Australia] :) I have been
>playing musical resistors for a week now, and no-one knows where I can get
>such resistors in ceramic form...

We get them from Digi-Key and like places here.  They really are very
common.  If there is a problem, I can get a bunch for people that really
have trouble getting them.  Australia is only as far as the post office... 

Cheers,

	Terry

>
>Thanks very much,
>
>:: Simon Yorkston
>:  Sole Proprietor of Liquid WebDesign
>:  http://www.liquiddesign-dot-org
>