Re: Capacitor Safety Discharge Method (fwd)

["Tesla list" <tesla@xxxxxxxxxx>]

---------- Forwarded message ----------
Date: Tue, 07 Aug 2007 01:41:31 -0700
From: Barton B. Anderson <bartb@xxxxxxxxxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: Re: Capacitor Safety Discharge Method (fwd)

Hi Ray,

Shorting caps is to keep you safe, yes. But shorting "charged" caps 
without bleeding them down causes plate forces within the cap = 
disforming the plates which reduces the caps integrity and C tolerance. 
Bleed charged caps first, then mechanically discharge in some fashion. 
The reasons are clear. Bleeders are not safety devices. So don't think 
of them that way. However, in numerous equipment they are often inserted 
by engineers as an attempt at safety (buyer beware). They are never the 
final word. If you rely on them for safety all can quickly go bad. None 
of this indicates they shouldn't be used, they just shouldn't be used as 
your safety line.

The only reason I posted to this thread was that someone said bleeders 
should never be used. That was probably not what was meant. He probably 
meant they should never be used as a safety line. However, I just didn't 
want coilers to think bleeders were a bad thing, because their not. They 
are often necessary.

In most of our TC circuits, our tranny's provide the bleeding action and 
only a shorting safety action is required before touching anything. 
There are "some" circuits that can retain a charge and then bleeders are 
definitely a good idea (not for safety, for cap health). Pretty simple 
logic.

Take care,
Bart

Tesla list 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?
>
>Ray
>
>On Aug 6, 2007, at 7:54 PM, Tesla list wrote:
>
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>>---------- Forwarded message ----------
>>Date: Mon, 06 Aug 2007 20:38:11 +0000
>>From: nancylavoie@xxxxxxxxxxx
>>To: Tesla list <tesla@xxxxxxxxxx>
>>Subject: Re: Capacitor Safety Discharge Method (fwd)
>>
>>Hi, Chris. Thats exactly what I was trying to get an answer to in the
>>previous posts and I think that if you kind of read between the lines 
>>in
>>Bart's reply, you can see that its probably okay to do if you use 
>>bleeder
>>resistors and discharge the cap after the charge has bled off. What I
>>wanted to use was a Ross Engineering relay rated at 40 kv (normally 
>>open
>>contacts) and wire it across the terminals of the capacitor and
>>resistors.It would then just be a simple matter of flipping a switch 
>>and
>>doing the work of the screwdriver in a much safer fashion.Anyone see a
>>problem? Wyatt
>>
>>-------------- Original message --------------
>>From: "Tesla list" <tesla@xxxxxxxxxx>
>>
>>    
>>
>>>---------- Forwarded message ----------
>>>Date: Mon, 06 Aug 2007 01:53:57 -0400
>>>From: Crispy
>>>To: tesla@xxxxxxxxxx
>>>Subject: Capacitor Safety Discharge Method
>>>
>>>Hello,
>>>
>>>In light of the recent discussion about the necessity of a manual
>>>discharge for the tank capacitor in addition to bleeder resistors, 
>>>I've
>>>been considering an easier method of manual discharge than the
>>>stick-a-screwdriver-in-the-spark-gap method for my coil. I was 
>>>thinking
>>>about an electronic method, and here's the idea. Would it be possible
>>>to have a linear pull-style solenoid with an electrode that, when
>>>powered, would retract its electrode from another static electrode, to
>>>act as the safety discharge? The normal state (no electricity applied)
>>>would be to have the contacts together, and the capacitor shorted. Of
>>>course, the electrodes would have to be insulated from the solenoid.
>>>Also, would it be possible to immerse this under oil, if the gap
>>>provided by the solenoid was insufficient to prevent sparking over in
>>>normal operation, or would the oil coat the electrodes and somehow
>>>prevent safety discharge?
>>>
>>>Thanks,
>>>Chris
>>>
>>>
>>>
>>>      
>>>
>>    
>>
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