Re: Capacitor Safety Discharge (my system) (fwd)

["Tesla list" <tesla@xxxxxxxxxx>]

---------- Forwarded message ----------
Date: Thu, 9 Aug 2007 07:57:14 +0800
From: Peter Terren <pterren@xxxxxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: Re: Capacitor Safety Discharge (my system)

I run a pulse cap bank for exploding wire, coin shrinking, pyrotechnics and 
general mayhem. It is a 16kJ capable bank which I have only ever run to 5kJ. 
Since I bolt things on and off the main electrodes frequently, I need to be 
100% sure of discharge.
I have the following:
A group of 4 neons connected via a resistor chain gives a bright visual 
indication of voltage but will extinguish at perhaps 200V
A single neon relaxation oscillator that flashes with voltage down to 70V
A meter showing total voltage
A shorting strap attached to a ? 60K 20W resistor
A spanner as a final pre-touch check.

I get nervous particularly when I am doing shots that don't give full 
discharge. You don't want to rely on one method alone if it is truly life 
threatening as this is.  I don't have a continuously connected bleeder 
resistor but leave the shorting strap with 60K resistor connected when not 
in use to prevent the recovered charge which would otherwise go to several 
hundred volts.

Peter
http://tesladownunder.com

>
> ---------- Forwarded message ----------
> Date: Wed, 8 Aug 2007 12:12:24 -0700
> From: Ray von Postel <vonpostel@xxxxxxxxxxx>
> To: Tesla list <tesla@xxxxxxxxxx>
> Subject: Re: Capacitor Safety Discharge Method (fwd)
>
> Jim:
> Sorry, your logic still escapes me.  How fast is the capacitor
> discharged if a resistor is open?   Yes, as you point out "There is a
> world of difference....", but what has that to do with safety?  I do
> not accept that there is any safe level of voltage when it comes to
> safety.  Perhaps you would care to state what voltage level is safe
> under all conditions but I don't.
>
> The bottom line is that resistors are fallible just as are O rings.
> Don't trust your life to them nor advocate something that could and has
> killed some one.
>
> The best safety device I know of is a suitable length of bare copper
> braid such as sometimes used to connect storage batteries, one end
> bolted permanently to one side of the capacitor bank (Ground?) and the
> other end attached with a mechanical fastener to a 1/4 inch brass rod
> bent with a hook on the end.  The brass rod is an extension on about 3
> feet of insulating plastic or fiber rod to use as a handle. It is easy
> to see that something like that is in working condition.  So it goes
> flash crackle pop.  So what if it keeps you or some one else from
> getting killed?
>
> I have had my say.  Now if anyone gets hurt because they refused to
> heed this waring they certainly deserve the appellation for which D.C.
> suffered flames, IDIOT!!!
>
> Ray
>
> On Aug 7, 2007, at 3:30 PM, Tesla list wrote:
>
>>
>> ---------- Forwarded message ----------
>> Date: Tue, 07 Aug 2007 15:27:37 -0700
>> From: Jim Lux <jimlux@xxxxxxxxxxxxx>
>> To: Tesla list <tesla@xxxxxxxxxx>
>> Subject: Re: Capacitor Safety Discharge Method (fwd)
>>
>> At 05:51 AM 8/7/2007, you wrote:
>>
>>> ---------- Forwarded message ----------
>>> Date: Mon, 6 Aug 2007 21:45:35 -0700
>>> From: Ray von Postel <vonpostel@xxxxxxxxxxx>
>>> To: Tesla list <tesla@xxxxxxxxxx>
>>> Subject: Re: Capacitor Safety Discharge Method (fwd)
>>>
>>> Guys:
>>>
>>> You are shorting out capacitors to keep from frying yourselves. What
>>> is
>>> the safety logic of putting some resistors in the circuit?
>>
>>
>> Small resistors limit the current when discharging, while still
>> getting the voltage low enough, quick enough, to be safe.  There's a
>> world of difference between dumping hundreds of joules in 1
>> millisecond vs dumping it in 1 second.
>>
>>
>>
>>
>>
>
>
>