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Can you treat "super" caps the same way as regular caps
to increase the voltage rating? For example, can you
wire three .33 farad 5 volt super caps in series to get
a 15 volt .1 farad capacitor?
Can you treat "super" caps the same way as regular caps
to increase the voltage rating? For example, can you
wire three .33 farad 5 volt super caps in series to get
a 15 volt .1 farad capacitor?
Can you treat "super" caps the same way as regular caps
to increase the voltage rating? For example, can you
wire three .33 farad 5 volt super caps in series to get
a 15 volt .1 farad capacitor?
Why did you say NO? Per what you posted below, the voltage rating
3 - .33 Fd 5 volt caps in parallel is equivalent to a 1 Fd 5 volt cap
3 - .33 Fd 5 volt caps in series is equivalent to a .11 Fd 15 volt cap
Jay
ehsjr@bellatlantic.net> wrote in message
news:3F28953B.BD485D81@bellatlantic.net...
Can you treat "super" caps the same way as regular caps
to increase the voltage rating? For example, can you
wire three .33 farad 5 volt super caps in series to get
a 15 volt .1 farad capacitor?
happyhobit wrote:
NO.
Why did you say NO? Per what you posted below, the voltage rating
does increase to 15, and the capacitance rating decreases to
.11 farad. (Is it the fact that I said .1 farad in my question?)
3 - .33 Fd 5 volt caps in parallel is equivalent to a 1 Fd 5 volt cap
3 - .33 Fd 5 volt caps in series is equivalent to a .11 Fd 15 volt cap
Jay
ehsjr@bellatlantic.net> wrote in message
news:3F28953B.BD485D81@bellatlantic.net...
Can you treat "super" caps the same way as regular caps
to increase the voltage rating? For example, can you
wire three .33 farad 5 volt super caps in series to get
a 15 volt .1 farad capacitor?
No problem - I just wanted to be sure I understood what youWell I could try to defend my answer by saying that the resultant cap would
be .11 and NOT .1, but the truth is I'm getting old and I missed the decimal
point. Sorry
Jay
ehsjr@bellatlantic.net> wrote in message
news:3F293318.23536CB6@bellatlantic.net...
happyhobit wrote:
NO.
Why did you say NO? Per what you posted below, the voltage rating
does increase to 15, and the capacitance rating decreases to
.11 farad. (Is it the fact that I said .1 farad in my question?)
3 - .33 Fd 5 volt caps in parallel is equivalent to a 1 Fd 5 volt cap
3 - .33 Fd 5 volt caps in series is equivalent to a .11 Fd 15 volt cap
Jay
ehsjr@bellatlantic.net> wrote in message
news:3F28953B.BD485D81@bellatlantic.net...
Can you treat "super" caps the same way as regular caps
to increase the voltage rating? For example, can you
wire three .33 farad 5 volt super caps in series to get
a 15 volt .1 farad capacitor?
Can you treat "super" caps the same way as regular caps
to increase the voltage rating? For example, can you
wire three .33 farad 5 volt super caps in series to get
a 15 volt .1 farad capacitor?
I believe that's exactly how they do the following, by putting caps inYou can't do that with any capacitor unless you parallel them
with resistors. Otherwise the voltage across each one would be set by
the leakage current.
On Thu, 31 Jul 2003 04:04:16 GMT, ehsjr@bellatlantic.net wrote:
Can you treat "super" caps the same way as regular caps
to increase the voltage rating? For example, can you
wire three .33 farad 5 volt super caps in series to get
a 15 volt .1 farad capacitor?
Of course you can. (Example below) Perhaps you have somethingYou can't do that with any capacitor unless you parallel them
with resistors.
At what point (how many ohms) does the leakage resistanceOtherwise the voltage across each one would be set by
the leakage current.
On Thu, 31 Jul 2003 04:04:16 GMT, ehsjr@bellatlantic.net wrote:
Can you treat "super" caps the same way as regular caps
to increase the voltage rating? For example, can you
wire three .33 farad 5 volt super caps in series to get
a 15 volt .1 farad capacitor?
ratman@execpc.com wrote:
You can't do that with any capacitor unless you parallel them
with resistors.
Of course you can. (Example below) Perhaps you have something
specific in mind?
Example using regular electrolytics:
Take a capacitive power supply filter using say 2 4700 uf
16 V caps in series on a 12 V DC supply with an AC input of
15 volts and full wave bridge rectifier. The peak voltage is
about 19.8 volts, and you have only 16 V caps. The reactance
of the caps in series (2350 uf) is about .56 ohms total; the
reactance of each cap is about .28 ohm. What resistance would
you put in parallel with each cap?
Otherwise the voltage across each one would be set by
the leakage current.
At what point (how many ohms) does the leakage resistance
become significant enough to require equalizing resistors?
Do you have something specific in mind?
On Thu, 31 Jul 2003 04:04:16 GMT, ehsjr@bellatlantic.net wrote:
Can you treat "super" caps the same way as regular caps
to increase the voltage rating? For example, can you
wire three .33 farad 5 volt super caps in series to get
a 15 volt .1 farad capacitor?
Yes - for safety, you need to put a bleeder resistor acrossSeries caps are mostly only used for high voltage apps.
Resistors are always used.
With super caps, I don't know. It seems logical that youDoing this with big electrolytics sounds
like a bad idea.
However, I have been told that at least some types of
supercaps have leakage matched from the factory (organic type). If
you are going to stack supercaps you would have to do the same or use
resistors. I have also been told that the resistor trick does not
work well with acid based supercaps, but I don't know why.
On Fri, 02 Jan 2004 05:40:20 GMT, ehsjr@bellatlantic.net wrote:
ratman@execpc.com wrote:
You can't do that with any capacitor unless you parallel them
with resistors.
Of course you can. (Example below) Perhaps you have something
specific in mind?
Example using regular electrolytics:
Take a capacitive power supply filter using say 2 4700 uf
16 V caps in series on a 12 V DC supply with an AC input of
15 volts and full wave bridge rectifier. The peak voltage is
about 19.8 volts, and you have only 16 V caps. The reactance
of the caps in series (2350 uf) is about .56 ohms total; the
reactance of each cap is about .28 ohm. What resistance would
you put in parallel with each cap?
Otherwise the voltage across each one would be set by
the leakage current.
At what point (how many ohms) does the leakage resistance
become significant enough to require equalizing resistors?
Do you have something specific in mind?
On Thu, 31 Jul 2003 04:04:16 GMT, ehsjr@bellatlantic.net wrote:
Can you treat "super" caps the same way as regular caps
to increase the voltage rating? For example, can you
wire three .33 farad 5 volt super caps in series to get
a 15 volt .1 farad capacitor?
I think there is another reason you need a resistor dividerYes - for safety, you need to put a bleeder resistor across
each series connected cap. If a cap in the series string
failed open, and you had a single bleeder across the series
string, no caps would be discharged by the bleeder. But with
a bleeder resistor across each cap, it wouldn't matter if
one cap failed open - the others would still discharge through
their own bleeder resistors.
Yes - for safety, you need to put a bleeder resistor across
each series connected cap. If a cap in the series string
failed open, and you had a single bleeder across the series
string, no caps would be discharged by the bleeder. But with
a bleeder resistor across each cap, it wouldn't matter if
one cap failed open - the others would still discharge through
their own bleeder resistors.
I think there is another reason you need a resistor divider
across caps in series. That's to make sure they each get their
share of the voltage.
You should never run an electrolytic near its voltage rating.Suppose one cap leaked a bit less than the other. Then it would
get more voltage and the other one would get less. Since they are
probably running near their voltage rating (or you wouldn't bother
putting them in series) that's probably not a good idea.
I agree that dirt or water would be a problem in a HV supply.Also, the leakage from dirt or water on your board could be
unbalanced too. If your board is clean today, it might get
dirty tomorrow. Or the layout might might not be balanced.
--
The suespammers.org mail server is located in California. So are all my
other mailboxes. Please do not send unsolicited bulk e-mail or unsolicited
commercial e-mail to my suespammers.org address or any of my other addresses.
These are my opinions, not necessarily my employer's. I hate spam.
Hal Murray wrote:
Yes - for safety, you need to put a bleeder resistor across
each series connected cap. If a cap in the series string
failed open, and you had a single bleeder across the series
string, no caps would be discharged by the bleeder. But with
a bleeder resistor across each cap, it wouldn't matter if
one cap failed open - the others would still discharge through
their own bleeder resistors.
I think there is another reason you need a resistor divider
across caps in series. That's to make sure they each get their
share of the voltage.
I put 10 470 uf 450 volt caps in series to get 47 uf
at 4500 volts. I use a 2500 volt xformer, yielding
~3500 volts peak, rectify it and apply it across
the series caps - which results in ~350 volts across
each cap. At 120 hz, each cap has a reactance of 2.82
ohms. How much leakage does a cap have to exhibit to
necessitate an equalizing resistor? What value do you
suggest for equalization?
Suppose one cap leaked a bit less than the other. Then it would
get more voltage and the other one would get less. Since they are
probably running near their voltage rating (or you wouldn't bother
putting them in series) that's probably not a good idea.
You should never run an electrolytic near its voltage rating.
Also, the leakage from dirt or water on your board could be
unbalanced too. If your board is clean today, it might get
dirty tomorrow. Or the layout might might not be balanced.
I agree that dirt or water would be a problem in a HV supply.
Show me the numbers that indicate the need for equalizing
resistors. How much dirt/water caused leakage do you have
in mind that would not require a different physical design
for safety reasons? What value equalizing resistors
would solve the leakage problem you have in mind?
--
The suespammers.org mail server is located in California. So are all my
other mailboxes. Please do not send unsolicited bulk e-mail or unsolicited
commercial e-mail to my suespammers.org address or any of my other addresses.
These are my opinions, not necessarily my employer's. I hate spam.
Top posted response. It does not show the question itFor HV, I think I've seen something like a few 100k used. You
might find a Radio Amateur's Handbook for more info.
On Sun, 04 Jan 2004 05:22:39 GMT, ehsjr@bellatlantic.net wrote:
Hal Murray wrote:
Yes - for safety, you need to put a bleeder resistor across
each series connected cap. If a cap in the series string
failed open, and you had a single bleeder across the series
string, no caps would be discharged by the bleeder. But with
a bleeder resistor across each cap, it wouldn't matter if
one cap failed open - the others would still discharge through
their own bleeder resistors.
I think there is another reason you need a resistor divider
across caps in series. That's to make sure they each get their
share of the voltage.
I put 10 470 uf 450 volt caps in series to get 47 uf
at 4500 volts. I use a 2500 volt xformer, yielding
~3500 volts peak, rectify it and apply it across
the series caps - which results in ~350 volts across
each cap. At 120 hz, each cap has a reactance of 2.82
ohms. How much leakage does a cap have to exhibit to
necessitate an equalizing resistor? What value do you
suggest for equalization?
Suppose one cap leaked a bit less than the other. Then it would
get more voltage and the other one would get less. Since they are
probably running near their voltage rating (or you wouldn't bother
putting them in series) that's probably not a good idea.
You should never run an electrolytic near its voltage rating.
Also, the leakage from dirt or water on your board could be
unbalanced too. If your board is clean today, it might get
dirty tomorrow. Or the layout might might not be balanced.
I agree that dirt or water would be a problem in a HV supply.
Show me the numbers that indicate the need for equalizing
resistors. How much dirt/water caused leakage do you have
in mind that would not require a different physical design
for safety reasons? What value equalizing resistors
would solve the leakage problem you have in mind?
--
The suespammers.org mail server is located in California. So are all my
other mailboxes. Please do not send unsolicited bulk e-mail or unsolicited
commercial e-mail to my suespammers.org address or any of my other addresses.
These are my opinions, not necessarily my employer's. I hate spam.
Here is some information: http://www.rubycon.co.jp/en/notes/index.htmlI agree that dirt or water would be a problem in a HV supply.
Show me the numbers that indicate the need for equalizing
resistors. How much dirt/water caused leakage do you have
in mind that would not require a different physical design
for safety reasons? What value equalizing resistors
would solve the leakage problem you have in mind?
I agree that dirt or water would be a problem in a HV supply.
Show me the numbers that indicate the need for equalizing
resistors. How much dirt/water caused leakage do you have
in mind that would not require a different physical design
for safety reasons? What value equalizing resistors
would solve the leakage problem you have in mind?
Here is some information: http://www.rubycon.co.jp/en/notes/index.html
see 6. Series Capacitor Connection
Stig Carlsson wrote:
I agree that dirt or water would be a problem in a HV supply.
Show me the numbers that indicate the need for equalizing
resistors. How much dirt/water caused leakage do you have
in mind that would not require a different physical design
for safety reasons? What value equalizing resistors
would solve the leakage problem you have in mind?
Here is some information: http://www.rubycon.co.jp/en/notes/index.html
see 6. Series Capacitor Connection
The site does not answer, and CAN NOT answer, the
question I asked. Please read it. I asked the poster
what HE had in mind. There is no way in hell
that a web site can answer what the poster had in mind,
the answer must come from him!
Next: the web site (yes, I did go to it) shows 2
200 volt electrolytics in series with 400 volts
applied. Run, do not walk, away from any site that
shows capacitors run right at their limit.
Next: the web site does not state that equalizing
resistors are *needed*. (The site calls them
"Voltage Distribution Resistors") At issue is
whether they are *needed* - what amount of leakage
does the poster have in mind?
The site states that they are *useful* to keep the
voltage across the capacitors the same. That's
true, but is not under discussion.