Jump to content
Sign in to follow this  
dryan

Capacitor

Recommended Posts

Your all nuts! Short the leads with a short peice of any small gauge wire or a few quick taps with a screwdriver is all you need to do. If the unit was denergized for any period over a few minutes, the internal circuitry has already dischraged most of the eneregy from the cap. All that will be left is some residual charge. 4,000 or 40,000 amperes at 1/100 of a second isn't going to melt a copper conductor anyway.

 

You're joking, right?

 

Discharging a capacitor - especially a large one - too quickly leads to very bad things. A large one like that can store a hell of a lot of charge which makes it even worse.

Share this post


Link to post
Share on other sites

I think BPHGravity is looking for a Darwin Award.

I'd trust Dave and swansont. I mean, even little capacitors can give you a nasty shock, so I'd expect a larger one to give you a very very nasty shock (or maybe death) if you tried.

Share this post


Link to post
Share on other sites
maybe death

 

maybe death? Did you say maybe? The proper word for it is, INSTANT!

Share this post


Link to post
Share on other sites

The capacitors also have a habit of blowing up :)

Share this post


Link to post
Share on other sites

They do??? Why? The amount of current that will pass through them?

Share this post


Link to post
Share on other sites

I think so; my dad's done it a couple of times by accident with fairly small capacitors. One this size might make a big bang :)

Share this post


Link to post
Share on other sites
The capacitors also have a habit of blowing up :)

 

That’s why I said point the side with the grooves away from you. The grooves are there to channel the debris.

 

And it would not likely cause instant death unless you have heart problems and you touch each lead with a different hand, and even then it’s not likely to cause death.

 

The only real reason for using a bleed resistor in this case would to prevent the oil vaporizing and thus exploding.

 

If you did happen to discharge a full charge through your hand it WOULD without a doubt leave burns and probably scars.

Share this post


Link to post
Share on other sites
They do??? Why? The amount of current that will pass through them?

 

They are filled with oil in an enclosed case so if it hapens to vaporize...

 

When I was younger I used to have fun blowing the small ones up. Most of the time it just cerates a little pinhole and you get a little smoke bomb but other times they completly explode in a cloud of white smoke.

Share this post


Link to post
Share on other sites

I deal with capacitors on a very frequent basis, so i am well aware of the dangers involved. My first post stated this concern very clearly.

 

The fact that I was trying to point out is that the origin and circumstance of the cap in question is known. It is being removed from a monitor that has been de-energized. Knowing this, per the requirements of NEMA/ANSI specifications and listing by UL, the cap is required to have a discharge circuit that reduces the voltage potential of the cap to under 50 volts in under one minute.

 

When a cap is pulled from a shelf or has an unknown orgin, OSHA recommends discharge through a 1 K ohm, 10-watt resistor for all caps up to 1,000V, 500uF.

 

My other point is that discharge through an insulated conductor will not "melt" the wire. Caps discharge in five time constants (TC). A TC=R*C. So if R = 0 then theoretically the cap discharges instantly. So it is important there be some resistance. How much resistance depends on how long a discharge time you want verse the size of the cap. For example a 300 micro farad cap discharged with a 100 ohm resistor would discharge in 5 * .0003 * 100 = .15 seconds.

 

An insulated copper conductor can withstand 1A for every circular mil for 5 seconds. Common #12 awg wire has 6,530 circular mils. So trust me when I say the wire will be fine.

Share this post


Link to post
Share on other sites

I just noticed... Two out of the four ads up top advertise high voltage capacitors. And yet it doesnt do anything when I click on them. Not very productive advertisments.

Share this post


Link to post
Share on other sites

I just realised that my post in here has been lost in that 2 day DB prob, Grrrr!

 

anyway, to recap (no pun intended).

here`s what I do with HV caps, at a 400v rating use a 150k resistor 1/4 watt is fine, in series with a small neon indicator bulb, solder that across the cap tags/leads.

you can still use the cap in your application without a problem also :)

but the neon striking voltage is 90v and breakdown at roughly 60v, it`ll provide a visible indication of when it`s safe to short it out and when it`s still too "hot".

it won`t effect the circuit the cap`s used in either :)

Share this post


Link to post
Share on other sites
I just noticed... Two out of the four ads up top advertise high voltage capacitors. And yet it doesnt do anything when I click on them. Not very productive advertisments.

At the bottom bar (in IE) it says something like:

goto whatever.com

so you type it in.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this  

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.