Rules for capacitors...

Htguy · 28th May 2005, 06:03 AM

Hi,

I am upgrading the caps in one of my projects and I have an 85vdc input and the caps I want to use (Wet Tantalum) are rated at 60vdc, if I use two caps in parallel I would add their capacitance together (C1+C2) but would that also mean that I could run up to 120vdc through them?

Thanks

God bless...

Mark

audiousername · 28th May 2005, 06:37 AM

No, paralleling caps will double capacitance but not double voltage rating. To double voltage rating, you will have to place them in series, which will halve their capacitance (assuming they are of identical value). Placing voltage equalising resistors across them may also be a good idea so that they share the voltage evenly.

Htguy · 28th May 2005, 03:01 PM

Hi,

it seems really strange to me that putting 2 60vdc caps in series would allow them to handle more voltage. Could you explain this to me?

Thanks

God bless...

Mark

kilowattski · 28th May 2005, 03:17 PM

It is simply physics. When putting them in parallel you increase the plate area but you still have the same voltage across each capacitor. When putting them in series, they will each handle part of the voltage but the plate area is decreased. If you think back to your AC theory course, I am sure you will remember. The rules are exactly opposite of the rules for resistors and inductors.

Here is a good site to help refresh your capacitor theory: http://www.oz.net/~coilgun/theory/capacitors.htm

Pay particular attention to the 3rd page "Multiple Capacitors".

jcx · 28th May 2005, 07:06 PM

it is a really stupid idea to series tantalum caps for more voltage

if the leakage and C ratio don't match exactly you will get unequal division of the voltage and with Tantalum caps the failure mechanism is to short circuit (at least until they catch fire due to power dissapation if the supply is stiff enough )

Do Not Use Tantalum caps where there is any possibility of exceeding their V rating

aside from the fact that Tantalum caps are highly distorting, mining tantalum has bad environmental and humanitarian consequences

modern low esr, long life Al electrolytics should meet any audio need

28th May 2005, 06:03 AM	#1
Htguy diyAudio Member Join Date: Aug 2003 Location: Tucson AZ	Rules for capacitors... Hi, I am upgrading the caps in one of my projects and I have an 85vdc input and the caps I want to use (Wet Tantalum) are rated at 60vdc, if I use two caps in parallel I would add their capacitance together (C1+C2) but would that also mean that I could run up to 120vdc through them? Thanks God bless... Mark

28th May 2005, 06:37 AM	#2
audiousername diyAudio Member Join Date: Jul 2004 Location: Melbourne, Victoria	No, paralleling caps will double capacitance but not double voltage rating. To double voltage rating, you will have to place them in series, which will halve their capacitance (assuming they are of identical value). Placing voltage equalising resistors across them may also be a good idea so that they share the voltage evenly. __________________ Jason

28th May 2005, 03:01 PM	#3
Htguy diyAudio Member Join Date: Aug 2003 Location: Tucson AZ	series caps... Hi, it seems really strange to me that putting 2 60vdc caps in series would allow them to handle more voltage. Could you explain this to me? Thanks God bless... Mark

28th May 2005, 03:17 PM	#4
kilowattski diyAudio Member Join Date: Aug 2003 Location: Long Island, New York	It is simply physics. When putting them in parallel you increase the plate area but you still have the same voltage across each capacitor. When putting them in series, they will each handle part of the voltage but the plate area is decreased. If you think back to your AC theory course, I am sure you will remember. The rules are exactly opposite of the rules for resistors and inductors. Here is a good site to help refresh your capacitor theory: http://www.oz.net/~coilgun/theory/capacitors.htm Pay particular attention to the 3rd page "Multiple Capacitors". __________________ ----------------------------------------------- Kilowattski

28th May 2005, 07:06 PM	#5
jcx diyAudio Member Join Date: Feb 2003 Location: ..	tantlum caps are Not a audio "Upgrade" it is a really stupid idea to series tantalum caps for more voltage if the leakage and C ratio don't match exactly you will get unequal division of the voltage and with Tantalum caps the failure mechanism is to short circuit (at least until they catch fire due to power dissapation if the supply is stiff enough ) Do Not Use Tantalum caps where there is any possibility of exceeding their V rating aside from the fact that Tantalum caps are highly distorting, mining tantalum has bad environmental and humanitarian consequences modern low esr, long life Al electrolytics should meet any audio need


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