Capacitor series confuses me

[lottathought]

I am probably missing something but I am really not getting this "Series" thing.
I have looked ..for a while but not finding anything answering my question.

I have read enough to know that some series can be substituted for others ...but I am not really getting why.
It looks like the series is maker specific.

I get that I have to replace a capacitor with the same uf...the same or larger Volts, size permitting ......and the same or better temp.
But I am at a loss as to how the series really fits into this.

Is it just a quality thing? If so, where do I find a list telling me the order of quality from lowest to highest?

Thanks

[mariushm]

Re: Capacitor series confuses me

Manufacturers make capacitors for decades now.

As technology improves they can refine their manufacturing processes to make better capacitors.

However, as some companies take advantage of some properties of the capacitors, the manufacturers have to keep making capacitors of the old type for some period of time (not to mention newer better capacitors are often more expensive because they have to recuperate costs and the production volume is small)

Also companies make capacitors that are suited for various purposes.. depending on how they're build and what chemical solutions are used in them, some capacitors can tolerate heat better, some tolerate big pulses of current, some are designed to keep energy in them for a long time, some are designed to be thin and long to fit small spaces and so on and so forth.

Manufacturers usually have series charts which show you what they think works best with what:

http://www.rubycon.co.jp/en/catalog/e_SERIES-CHART.html

http://www.nichicon.co.jp/english/pr...ini/pict_f.htm

The capacitors that often die in motherboards and power supplies and monitors are designed to be "low esr" / low impedance and have relatively high current ripple capability, meaning they have a low internal resistance and can handle the way these switching power supplies work, which is by sending pulses of energy 50-100 thousand times a second through the transformer.

So when you have to replace a capacitor, you have to look up what that capacitor you replace was designed for (or guess based on where that capacitor was placed in the circuit).
Then, you have to pick a capacitor from the same manufacturer or from another manufacturer that is close in technical characteristics to the old capacitor.

The reason for this is because in some cases, the company that made that circuit relied on the fact that the capacitor has its internal resistance within a certain range and "tuned" the circuit to use that. If you put a capacitor that has its resistance outside that range, the circuit can be unstable.

Just the same, the company selected that capacitor knowing it will handle/tolerate a certain amount of ripple current, so your new capacitor should be able to support an amount very close to the old capacitor's value, but ideally more.

So let's have an example...

Let's say you found a bad Nichicon PW capacitor, 330uF 25v

You go to the datasheet and look up at the description and the characteristics:



Miniature Sized, Low Impedance,
For Switching Power Supplies

10 x 16
0.14 ohm impedance at 100kHz
800 mA ripple current.

So I know it's for switching power supplies, so I'm going to look for "low impedance" capacitors, which have 0.068 ohm or less impedance , and 1050 mA or more impedance.
I want to get 470uF - it's important to keep capacitance the same most of the time - but I may be able to choose 35v or 50v as long as the new capacitor will fit on the board.
Let's say I may have up to 12.5mm in diameter on the board.

Looking at the Rubycon page that I linked above, since the capacitor is for switching power supplies, I know I have to look at the low impedance section and at the top I see ZLG, for example:

https://cdn.badcaps-static.com/pdfs/...3bb75aa682.pdf

Load Life: 105℃ 1000～5000hours. Ultra Low impedance.
FEATURES
・Extremely reduced impedance at high frequency range than ZL series.
・Load Life : 105℃ 1000～5000 hours.

This is a bit worrying.. you see, PW is just "low impedance" and this series is "ultra low impedance". But let's look at the table below to see if there is a 470uF 25v and what specs are there:

470uF 25v 8x20 1600mA 0.020 ohm

So it's smaller in diameter so it will fit, it can handle 1600mA which is more than the old one, so it would work, but the impedance is kinda low at 0.02 (original had 0.14). Not good.

Going down a bit on the chart, I see there a YHF:

https://cdn.badcaps-static.com/pdfs/...054e31a9da.pdf

470uF 25v 10x16 0.12 ohm impedance 770mA ripple

770mA is really close to 800, so in a pinch I would use this, and 0.12 ohm is also close enough (and lower) than 0.14 to not worry about it.

If I'm sure I can fit 20mm tall capacitor, I could select the 35v capacitor in the same series, which has 0.078 ohm impedance and 1050mA ripple. 0.078 would be a bit low, but it's still close enough to 0.14 that it shouldn't be a problem.

It may be a problem if I'd select a capacitor from series that has impedance 0.02-0.05 ohm impedance for example.

Once you find something suitable, you can of course look around to see if another series has similar specifications but is designed to tolerate heat better, which means longer life

[lottathought]

Re: Capacitor series confuses me

This is a lot to wrap my head around. But I think I am starting to get it. I am going to go over your post a couple more times to get it locked in. Thanks so much for this. It really helped.

[mariushm]

Re: Capacitor series confuses me

Ok, that's cool. if you have any questions ask away.

Re-reading my post, it jumps out to me that I forgot to edit a couple of lines:

Let's say you found a bad Nichicon PW capacitor, 330uF 25v

This is supposed to be:

Let's say you found a bad Nichicon PS capacitor, 470uF 25v

I initially wanted to make the example with Nichicon PW 330uF 25v, but it was easier to explain with that Nichicon PS 470uF 25v capacitor.
The link to the datasheet just below this line is the correct one, for Nichicon PS.

Also, a couple of paragraphs below:

This is a bit worrying.. you see, PW is just "low impedance"

should read as

This is a bit worrying.. you see, PS is just "low impedance"

Sorry if it confused you. I'm afraid posts can't be edited anymore, after a while.