Electrolytic caps in series - Page 2

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Re: Electrolytic caps in series


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Inability to raise even the slightest meaningful rebuttal containing even
a smidgen of proof noted .
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  nothing of any value noted here either , you really must learn to be
truthful or continue to expect honest critism
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  I read it and made the right decision
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  Thanks for admiting your wrong toaster boy.
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Re: Electrolytic caps in series



"Uncle-Fester"   =  another anencephalic prick



 **  Fuck off   -  you rote learning moron.




..........  Phil



Re: Electrolytic caps in series


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  make me you weak insipid little toaster boy
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Re: Electrolytic caps in series



"Uncle-Fester"   =  another anencephalic prick


 **  Fuck off   -  you rote learning moron.




..........  Phil




Re: Electrolytic caps in series


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Sorry I cant hear you very well at all
  perhaps removing roddles dick from your mouth might help you
articulate toaster boy ?

Re: Electrolytic caps in series



"Uncle-Fester"   =  another anencephalic prick


 **  Fuck off   -  you rote learning moron.




..........  Phil





Re: Electrolytic caps in series


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Sorry roddles , what's that you say ?
  hard to hear  over your spanking the monkey so furiously .

Re: Electrolytic caps in series



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Good god, someone has cloned Rod Speed!

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   yeah Buddy!, only with Horns!!!

Re: Electrolytic caps in series


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But very very tiny ones ,( worn off due to abuse)

Re: Electrolytic caps in series




 One day Uncle-Fester got dressed and committed to text

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OK, since you guys say you have the real 'gen' (not like Phil) and all the
knowledge, how do ya calculate the values of the resistors ??
Forget all the abuse and denigration, share your superior knowledge with me
??

--
Regards ..... Rheilly Phoull



Re: Electrolytic caps in series



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For resistors across electros in series??: it's in that link I posted.
for resistors in series it's R(total)= r1+r2+r3......+rn
for resistors in parallel it's R(total) = 1/(1/r1 + 1/r2 + 1/r3 +..1/rn)

Regards
Mark

Re: Electrolytic caps in series


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What you do is calculate the bleeder resistor value based on the
following worst case conditions:
- The maximum voltage rating of one one of the caps
- Assuming one cap has maximum leakage and the other has zero leakage

i.e. The capacitor with the leakage with drag the mid rail voltage away
from it's nominal half rail, creating a greater voltage across the cap
with no leakage. You don't want to have more than the maximum capacitor
voltage across the non-leaky cap.

Once you assume these worse case conditions then the circuit is easy to
analyse.

Each resistor is:
R=(CapLeakRes * (MaxCapVolt-(Vrail/2)) / (Vrail-MaxCapVolt)) * 2

The leakage will be voltage dependant, but this a simple way to look at
it.

Hope that helps.

Regards
Dave :)


Re: Electrolytic caps in series



"David L. Jones"

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**  The scenario concerns *identical, new electro* caps being used as post
inductor filters.


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 **  Why not assume the earth is flat while you are at it??


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**  You forget the caps are in series   -  so any current MUST be identical
in both caps at all times !!!


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**  I got news for you David -  if an electro shows little or no leakage,
then it is well able to stand the applied voltage.


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**  Shame all your assumptions are false.






...........     Phil





Re: Electrolytic caps in series


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It's called calculating for worst case conditions, it's a perfectly
valid way to calculate bleeder resistors.

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Not when you put bleed resistors across them! That's what we are
talking about.
If the leakage of a capacitor changes then the mid rail voltage will
change also, thus increasing the voltage across the other cap. It ain't
a simple series circuit any more when you put bleeder resistors in
PARALLEL.

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Bleeder resistor values are always calculated using ball-park figures
and typical expected worst case conditions. In this case one cap could
be leaky and the other cap may not have any leakage, how is that a
false way to view this circuit?
The question was how to calculate bleeder resistor values for series
caps, not if they are needed or not. I gave an answer for calculating
bleeder resistor values, how would you calculate it Phil?

Dave :)


Re: Electrolytic caps in series



"David L. Jones"
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**  No electro has zero leakage and the  "maximum"  cannot be found except
by testing a huge number of caps.


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 **  Not with your totally mad assumptions.


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** Learn to read David,  the current flowing in  series connected caps must
be identical.


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**  Go back   -  you have jumped a crucial step.


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 **   Correct -  the problem is your assumptions about these matters are
wacky.


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**  Zero leakage electros do not exist.

  You are pulling wild assumptions out of mid air.


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**  The two questions are not separable.

You need realistic figures for the leakage performance and leakage v voltage
curve of the ACTUAL caps in question BEFORE any calc can be done.



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**  You gave a  ** bleeding stupid ** one  -  I doubt a *digital* person
like you has ever worked on gear with more than a 15 volt supply in your
life.

Do you claim to have any engineering experience with high voltage electros
??


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**  My position is that the OP does not need any in **his** app -  if done
as I suggested with new, identical caps that have a 30 % or more margin of
voltage.

  "  **  Forget it  -  just use caps that have a large margin in excess of
the
needed voltage.

 Eg  -  two 350 volt types applied to a 500 volt supply.

The caps will very soon reach a mutual, acceptable agreement on what
precise voltage suits their individual taste !!   "

The reason I said this is that I have done it at least 100 times with 350
and 400 volt caps from WES and Farnell and in every case the resulting
centre voltage was within 5% of half supply.

There are OTHER situations where bleed resistors might be very worthwhile or
even essential  -  ie on the first stage after the rectifier where the caps
may undergo significant ripple current and hence self heating.




...........     Phil











Re: Electrolytic caps in series


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Yep, that's why the question is relevant and I gave a way to calculate
the values, as asked.
How you get the "worst case" or "best case" leakage values doesn't
change the formula presented, or the way you calculate it.

You still haven't told us how you would calculate the values Phil.

Dave :)


Re: Electrolytic caps in series



"David L. Jones"

( snip lots of good stuff that DLJ rudely ignored)


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** The OP has a specific case in mind  -  but being a novice he asked an
overly general question thinking it would contain the answer he needed.

NG posters do that over and over and over  -  then wind up with a totally
useless answers from pedantic fuckheads like David L Jones who must
**insanely** imagine he has been presented with an some problem to solve
!!!



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** So you deny posting this ?

"  What you do is calculate the bleeder resistor value based on the
following worst case conditions:
- The maximum voltage rating of one one of the caps
- Assuming one cap has maximum leakage and the other has zero leakage.   "


** The info you supplied is utterly useless to the OP as he has no idea what
leakage figures to use.

 Apparently  -  since you are a digital tech using 5 volt supplies -
neither do you.


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**  You rudely ignored what I posted on that question:

" You need realistic figures for the leakage performance and leakage v
voltage
curve of the ACTUAL caps in question BEFORE any calc can be done.  "

You also need to know all about the application and determine if the DC load
current of the bleed resistors is acceptable at all   -  in the OPs one,
the original caps had no bleed resistors and additional DC current would
significantly disturb supply voltage values and increase supply ripple so
that it became audible as hum.





...........    Phil




Re: Electrolytic caps in series



"Phil Allison"

**correction:
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Re: Electrolytic caps in series


put finger to keyboard and composed:

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Series caps are often used in dual voltage PSUs. Here is a typical
circuit with balancing resistors:
http://www.pavouk.comp.cz/hw/atxps.png


- Franc Zabkar
--
Please remove one 's' from my address when replying by email.

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