On Tue, 6 May 2014 22:37:02 -0700 (PDT), Bill Sloman Gave us:
The FACT that they are the de facto standard in HV current limiting does change calling you an idiot to a fact. Though it was already a fact before that statement revisited the observation. You ARE an idiot. You ARE rubbish. You are a goddamned, retarded, interloping twit, with practically nil actual knowledge.
Decadent idiot wrote in :
Your just a decadent idiot :-)
Are clues that expensive over there?
On Wed, 07 May 2014 06:58:48 GMT, Jan Panteltje Gave us:
"your"?
You, JanTard, are a complete moron.
It depends on the rise time.
If you can establish the hot channel - and kill the high voltage - at the right speed enough, there isn't enough energy deposited in the resistors to blow it apart.
Not that AlwaysWrong can be expected to be aware of this.
you tried.
It took near kilovolt stress levels to establish the hot channel. Once it was there, the kilovolts bled away.
You'd have to be really stupid not to realise this, but you are AlwaysWrong.
Actually, you are, and this means that you think that anybody disagrees with you is both foolish and wrong, which is very rarely true.
Like I said. Old-fashioned. And what distinguishes "consumer grade" Geiger-Muller tubes from the antique over-priced rubbish that you sell to the military?
Do let us see how thoroughly you've master the physics of self-quenching gas-phase avalanche discharges.
The fact that they may be the "de facto" standard in the antiquated branch of the industry that you inhabit doesn't prevent them from being cheap rubbish. In fact your endorsement of them as a "de facto" standard reinforces the argument.
And AlwaysWrong claiming that anybody else has "practically nil knowledge" has a certain rococco charm. It isn't as if you'd know.
On Wed, 7 May 2014 01:55:46 -0700 (PDT), Bill Sloman Gave us:
Goddamned long line retards like you should be banned from all of Usenet!
Dumbfuck. The statement was about FILM resistors, idiot!
They fail open pretty readily. Your remark is true for the bulk variety, which is why they get used in said circumstances.
The typical "flatso" type HV resistor is NOT meant for ANY kind of impulse absorption. They are meant for feedback strings and bleeders.
Since you like Obama so much:
So, this is in pressurized SF6? or in air? So, your 20 seconds at
6 kv is causing internal corona or arcing? My calculation is that is at 1.6 W, so it sounds like these resistors are not handling even near to rated conditions.Jon
The other way to do it is a Pellatron. It has chains of alternating plastic and metal links that are charged by lower voltage power supplies via brushes. The links carry charge up to the center terminal. Notre Dame physics has a 10 Mv unit. Oak Ridge used to have a 50 Mv folded tandem accelerator, but it has been shut down for budgetary reasons.
Jon
We are also supposed to respect the inadequacies of the software that you use to access the Usenet? Maybe you'd prefer we made our marks in wet clay, baked it, and air-dropped the shards on your archeological reconstruction of the Babylonian Usenet?
It's true about all resistors made with a negative temperature coefficient of resistance resistive material, film carbon, bulk carbon and NTC thermistors.
The fact that they frequently fail open isn't relevant to the observation that they *can* fail to short circuit.
But if you over-volt the whole string, the fact that some of the resistors can fail short, putting progressively higher voltages across the rest of the resistors in the string that haven't yet failed, makes for a potential impulse load.
Actually at a little over 5K they are registering on the RGA but no damage. I suppose over time it would kill them, but at 6K the phenolic just does a split! WHen I said pressure, I would referring the pressure inside the phenolic package when it went pow! :)
Jamie
The Caddock thickfilms are certainly not carbon.
A high value carbon comp is a little carbon and a lot of organic binder. High voltages might eventually start carbonizing the binder. Thickfilms are metallic oxides, different physics. People sell really high-voltage thickfilm resistors.
If you buy a resistor that's designed and rated for high voltage use, it just might be more reliable that a carbon comp that's not.
So call Caddock and talk to them, or buy a crate full of Chinese carbon comps.
Buy a bunch of those red epoxy cylindrical HV ceramic caps. Charge one to 30 KV and sit it down on the garage floor. Change another one to 30 KV and sit it on top. Repeat.
Splitting down the center for a NTC material makes sense, (Bill's point.) It losses heat at the surface, and as it over heats, the hotter center conducts more and more.... til it can't..
George H.
A.
possible.
composite resistors
Not on carbon composition resistors. More like 10%. Carbon film could that kind of tolerance.
?-)
circuit,
adjacent
and
resistance go
for high
thin film
would
art.
Yep, Caddock is still a respected HV resistor manufacturer IIRC.
?-)
point
bags
know
Several very good points.
?-)
In some parts, not in others. It is a large area after all.
?-)
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