Equivalent capacitor

[chibitul]

Hi,

I need an electrolytic capacitor, 100V/35uF. I don't have one right
now... can I use two in series, let's say 50V/68uF? The equivalent
capacity should be 34uF, and since they are in series, the maximum
voltage 100V.

Thanks

 

[Ken Weitzel]

Hi,

I need an electrolytic capacitor, 100V/35uF. I don't have one right
now... can I use two in series, let's say 50V/68uF? The equivalent
capacity should be 34uF, and since they are in series, the maximum
voltage 100V.

Thanks

Hi Chibutul...

I think I'd much sooner see two 17's in series...

However, two caps in series isn't nearly as efficient
so while you're rounding, round up.

Which may (probably will) leave you with linearity problems,
so were it my set I'd keep on looking for a 34 at greater
than 100 volts.

Take care.

Ken

 

[Travis Jordan]

I think I'd much sooner see two 17's in series...

I think Ken meant "two 17's in parallel".

 

[Ken Weitzel]

I think Ken meant "two 17's in parallel".

Hi Travis...

Arghhh. Very kind of you, but I just goofed.
Silly old stroke damaged guy here.

Forgot that series capacitance is the reciprocal
of the total of the reciprocal of each cap in the
series.

Have to learn to think more, and type less

Apologies to the op, and to all.

Ken

 

[Dave Plowman (News)]

I need an electrolytic capacitor, 100V/35uF. I don't have one right
now... can I use two in series, let's say 50V/68uF? The equivalent
capacity should be 34uF, and since they are in series, the maximum
voltage 100V.

Why not just go for 47µF 100v? They're common enough, and electrolytics
are rarely critical in size.

 

[sofie]

Absolutely agree...... a most common value of 47uf @ 100V should
work perfectly in almost all applications calling for 35 uf @ 100V

 

[Pierre]

Could work, depending on the circuit it is mounted.
When you put electrolytic capacitors (Aluminium, Tantalum, ...) in series
you must put resistors in parallel in order to compensate the leakage
currents (10 times the leakage current value in the resistors) and balance
the transient voltages.
If you don't do that, the first time the voltage is applied to the two caps,
each capacitor won't see the same voltage and the rating may be exceeded.
Shall I remind you that an overloaded capacitor may explode ?

Better to wait for the good value.

 

[NSM]

Hi,

I need an electrolytic capacitor, 100V/35uF. I don't have one right
now... can I use two in series, let's say 50V/68uF? The equivalent
capacity should be 34uF, and since they are in series, the maximum
voltage 100V.

47 UF/100 Volts $0.35

http://www.allelectronics.com/matrix/Radial_Electrolytic_Cap.html

N

 

[Sam Goldwasser]

Hi Chibutul...

I think I'd much sooner see two 17's in series...

OK, we know you meant parallel.

However, two caps in series isn't nearly as efficient
so while you're rounding, round up.

Which may (probably will) leave you with linearity problems,
so were it my set I'd keep on looking for a 34 at greater
than 100 volts.

It's not the efficiency or linearity that would be the main issue
with capacitors in series. The problem is that if the leakage
resistances and capacitances are not the same, the voltage across
the two caps with not be equal. So, use a higher voltage to be
on the safe side if the application really requires close to
the working voltage.

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[Tom MacIntyre]

Hi,

I need an electrolytic capacitor, 100V/35uF. I don't have one right
now... can I use two in series, let's say 50V/68uF? The equivalent
capacity should be 34uF, and since they are in series, the maximum
voltage 100V.

Thanks

Just in case you are ignoring your earlier post, and sorry to
nag...you likely want 100uF, 35V.

Tom

 

[chibitul]

Yes Tom, thanks again. I do not ignore my threads, then why would I ask
here the experts? I made a mistake, now I found the exact capacitor and
I would like to install it but my wife has other plans for the
evening... well, tomorrow (maybe).

Thanks again, and BTW, you better "nag" than let someone stupid like me
install the wrong capacitor.

 

[Asimov]

"Tom MacIntyre" bravely wrote to "All" (13 Jul 05 21:32:12)
--- on the heady topic of "Re: Equivalent capacitor"

TM> From: Tom MacIntyre <[email protected]>
TM> Xref: aeinews sci.electronics.repair:53130

Hi,

I need an electrolytic capacitor, 100V/35uF. I don't have one right
now... can I use two in series, let's say 50V/68uF? The equivalent
capacity should be 34uF, and since they are in series, the maximum
voltage 100V.

Thanks

TM> Just in case you are ignoring your earlier post, and sorry to
TM> nag...you likely want 100uF, 35V.


Tom,

That is exactly what I was going to say. 35uF is a pretty oddball
capacitance value but 35 WVDC is a very common voltage rating.
Hey, who ever heard of a 17uF electro anyways, (besides the weird
old Philips stuff from Europe), ?

A*s*i*m*o*v

.... ELECTRON COPS STAGE COMPONENT RAID....SEVERAL CAPACITORS CHARGED!

 

[Tom MacIntyre]

Yes Tom, thanks again. I do not ignore my threads, then why would I ask
here the experts? I made a mistake, now I found the exact capacitor and
I would like to install it but my wife has other plans for the
evening... well, tomorrow (maybe).

Thanks again, and BTW, you better "nag" than let someone stupid like me
install the wrong capacitor.

Tom

 

[Jamie]

Hi,

I need an electrolytic capacitor, 100V/35uF. I don't have one right
now... can I use two in series, let's say 50V/68uF? The equivalent
capacity should be 34uF, and since they are in series, the maximum
voltage 100V.

Thanks

yes