IEFF question

[large_ghostman]

Before i ask my question, I want to relay something that has just happened. I won an auction on ebay a couple of weeks ago. The auction was for a large box of electrolytic capacitors, some new some used. There were alot of very large ones in the pictures, I won it for £2 . It came today and inside a large box was several very big jiffy bags, insides the bags was a jumble of capacitors, some in packets and alot loose. I dived in and started pulling them out, one looked really interesting! A large electrolytic 22000uF! 400V!!! 19A. I started looking at it to try and get the manufacture details for a datasheet, dad walks in and snatches it off me, straight out of my hands!!!!
This really annoyed me, that was until dad put the DMM on it, turns out alot of the very large used caps had not been discharged! So i have been blindly putting my hands in a bag full of caps charged upto 400V!!!
I think I have been lucky, but i am so annoyed someone would pack them like this. RANT OVER

anyway the question, What is the IEFF on a electrolytic capacitor? for example the one I have in my hand (now discharged with a resistor screwed across its terminals) say's I EFF(100Hz) 19A (50C)

 

[ericgibbs]

Look here.

 

[cowboybob]

You dodged a bullet on that one, LG....

Keep in mind that electrolytics (and, famously, CRTs) can gain an electrostatic charge just sitting around.

 

[large_ghostman]

Thanks Eric, I assumed it related to something else. Yes CB I made a mistake and was lucky that dad was on the ball! I think that is why he has screwed the resistor on the terminals, so it dosnt keep a charge, We found one huge one with 600V sitting on it at 2200 uf!
No idea why I thought the person that sent them would make sure they were safe first! dad just slit the bags open and spread them on the bench, he then went through them one by one and tested for a charge. They will only have a max of 24V when in use, but when not in circuit the large ones will stay with a resistor on. Dad got a large shock last year of a psu primary side cap . That was a good day for learning bad words

 

[JimB]

but i am so annoyed someone would pack them like this.

Two possibilities,
the person sending the caps did not know any better,
or,
the idiot sending the caps thought it would be a jolly jape to charge them up first!

While I have known of this effect/problem for a long time, I may not think about putting a shorting link on a large capacitor.
It is quite common to see large capacitors with a shorting link when offered for sale at electronic junk sales.

An experiment:
Charge one of your large capacitors to (say) 24 volts. Leave it connected to the supply for a couple of minutes.
Disconnect from the supply and short the capacitor terminals for 5 seconds. Remove the short circuit.
Connect a voltmeter to the capacitor and watch the voltage rise, maybe not all the way to 24v, but it will rise.

The effect is due to energy stored in the dielectric between the capacitor plates.

JimB

 

[large_ghostman]

All the large caps over 16V have screw terminals, so dad has screwed a 10K resistor on them to keep them shorted. He has also confiscated all caps over 45V, until I need them and he is with me. Bloody parents
He called the guy and apparently they were in a room he was clearing out after a relative died, and he just sent as was.
By the way I have been looking at radio's, Looks like I would need way more money than I thought.

 

[JimB]

As a follow up to a PM discussion on radios:

He has also confiscated all caps over 45V

In that case don't tell him the PA anode voltage in an FT401, he will have kittens!

JimB

 

[large_ghostman]

As a follow up to a PM discussion on radios:

In that case don't tell him the PA anode voltage in an FT401, he will have kittens!

JimB

Thats ok Jim, he wont mind that the PA anode voltage is around 50V enough said

 

[dr pepper]

I think IEFF is justa fancy word for ripple current, if you were using a cap as a smoothing cap in apsu then the ripple current is an important factor, if you exceed it the cap will heat up and bang.
One place I worked at thought it was funny to charge up a motor start cap on the mains and then toss it too me, I threw it back at him and said it was the shock that made me do it, it wasnt.
People at mullards have been sacked for pulling similar stunts.
I received a clout from my dekatron clock the other night, its only a 47n but with 420v across it, it flippin well hurts.

 

[large_ghostman]

Yeah some of these caps were 22000uf with 100V, also a 400V one not sure the uf now. But alot of them had alot of charge in them. Not sure how I didnt get a wallop, I was just sticking my hand in and pulling the caps out, bit stupid really I should have thought about it first. One or two of those caps could have seriously hurt

 

[dr pepper]

While working on control panels I wear thin insulative gloves, if you were working on mains powered smps's these are a good idea, or anything that isnt powered by an isolation trans.