Ripple Current and ESR

[Chris]

Hi all,

What's the deal with this? I read somewhere that a high ripple current
figure for an electrolytic is a bonus; an expensive and sought-after
characteristic. However, I'd always thought ripple was anathema to PSUs.
Can some expert kindly explain the relationship between ESR, ripple
current, capacitor ageing and whatnot?

thanks.

 

[Jasen Betts]

On 2017-06-18, Chris <cbx@noreply.com> wrote:

Hi all,

What's the deal with this? I read somewhere that a high ripple current
figure for an electrolytic is a bonus; an expensive and sought-after
characteristic. However, I'd always thought ripple was anathema to PSUs.
Can some expert kindly explain the relationship between ESR, ripple
current, capacitor ageing and whatnot?

It means that it withstands a high ripple current.

--
This email has not been checked by half-arsed antivirus software

 

[Chris]

On Sun, 18 Jun 2017 19:35:44 +0000, Jasen Betts wrote:

On 2017-06-18, Chris <cbx@noreply.com> wrote:
Hi all,

What's the deal with this? I read somewhere that a high ripple current
figure for an electrolytic is a bonus; an expensive and sought-after
characteristic. However, I'd always thought ripple was anathema to
PSUs.
Can some expert kindly explain the relationship between ESR, ripple
current, capacitor ageing and whatnot?

It means that it withstands a high ripple current.

What's to "withstand"? Electroytics are designed to smooth that out,
after all.

 

[Phil Allison]

Chris wrote:

--------------

What's the deal with this? I read somewhere that a high ripple current
figure for an electrolytic is a bonus; an expensive and sought-after
characteristic. However, I'd always thought ripple was anathema to PSUs.
Can some expert kindly explain the relationship between ESR, ripple
current, capacitor ageing and whatnot?

** Ripple current is simply the RMS value of the current flowing into and out of a capacitor as it charges and discharges - something it must do in order to smooth rectified AC.

The current's magnitude depends on the p-p ripple voltage and the value of the cap and is somewhat greater than the DC load current.

Ripple current heats the cap according to "I squared R" where R is the actual ESR at the frequency and temperature of operation. So a low ESR cap has a higher ripple current rating.

However, I have not come across a electro cap where operation at 100Hz and with the usual 10% to 15% ripple voltage exceeds its ripple current rating.

When an electro cap is used on the OUTPUT of a SMPS the rating becomes more important as the ripple voltage at high frequencies can be small while the current is large. Luckily the ESR of a electro caps improves at high frequencies and also when the temperature rises.

Electro cap life is normally a function of operating temperature, halving for each 10 degrees C rise above room temp. It is purely due to the liquid electrolyte escaping from the cap as vapour - a few molecules at a time.

Manufacturers use about 3 time more electrolyte than needed inside electros so the cap will have a long life without change is ESR or capacitance until nearly all the electrolyte is gone.


..... Phil

 

[David Eather]

On Mon, 19 Jun 2017 07:14:31 +1000, Chris <cbx@noreply.com> wrote:

On Sun, 18 Jun 2017 19:35:44 +0000, Jasen Betts wrote:

On 2017-06-18, Chris <cbx@noreply.com> wrote:
Hi all,

What's the deal with this? I read somewhere that a high ripple current
figure for an electrolytic is a bonus; an expensive and sought-after
characteristic. However, I'd always thought ripple was anathema to
PSUs.
Can some expert kindly explain the relationship between ESR, ripple
current, capacitor ageing and whatnot?

It means that it withstands a high ripple current.

What's to "withstand"? Electroytics are designed to smooth that out,
after all.

the capacitor is not perfect - it also has internal resistance (and
inductance). As ripple current flows in and out of the capacitor it causes
heat via the internal resistance. To much heat and the service life is
short. Way too much heat and it vents messy crap all over the place.

--
Using Opera's mail client: http://www.opera.com/mail/

 

On Sunday, June 18, 2017 at 10:24:06 AM UTC-4, Chris wrote:

Hi all,

What's the deal with this? I read somewhere that a high ripple current
figure for an electrolytic is a bonus; an expensive and sought-after
characteristic. However, I'd always thought ripple was anathema to PSUs.
Can some expert kindly explain the relationship between ESR, ripple
current, capacitor ageing and whatnot?

thanks.

Very nice explanations!

 

>"Very nice explanations! "

Yeah Phil beat me to it and probably did a better job, except for explaining the actual power dissipation of the cap in question. Really, it is as simple as Ohm's law except you need an accurate RMS current factor.

In service I found out a few things about the engineering of newer TVs, annd this also means computer main boards. They use banks of caps, mainly to get that ripple current handling capacity.

I have serived so many TVs that were dead but the customer failed to mention that there was a dark part of the screen or some shit, or lines that I no longer replaced the banks of caps for testing. I found that just replacing one would do the trick and at least get it alive. It is amazing how these sets can suck the life out of three 3,300 uFs in a matter of years.

I think part of it is the quality of the caps because in this respect, my sister has this monitor wound up needing something ay 35 volts but I only had 25 volters, so I put in a twenty year old 100/160 which of course worked. I expected to have to order the right cap soon but the thing worked for years. YEARS.

But in servicing, if you are going to do it, look to see what caps are in banks. You might have a bank of five 1000s on one one, to get the thing alive you only need to replace (or just bridge) one. Once you confirm proper operation and the estimate is OKed then you go on and replace them all. I actually kept a bunch of caps at the bench for that purpose and never cut the leads down. With the long leads they "fit" where they never would, but they fit the circuit well enough to make it work.

we tried to avoid doing a total repair in the estimate stage but that is almost impossible. Even in the old RPTVs they could have a screen burn and the customer could be a prick about it. The laws here are very servicer unfriendly. I am glad to be out of it, but do seek to do something.

And if they had a dead set and a week later they have a screen problem, they think the whole thing is under warranty. Actually that is why every repair became $300 even when we only put in a three buck part, if that.

I tried to reason with people and draw an analogy to cars. If I fix the transmisssion on our car is are the brakes under my warranty ? Hell no. Neither is the radio. People flat out argued against that. My pussy boss let them get away with alot of shit and he got scammed more than once. I once told him he could have made twice the money, ut for whatevber reason he did not have the fight.

We lost a TV temporarily, the customer sued for $800 which is MAYBE what it would be worth working and in pristeen condition. We found the TV and he called the to let them know. they told him "OK we will drop the suit so you don't have to bother going to court" and then they showed up and won the default judgement.

This is a country of fucking scam artists. the kid (younger) has a job at lube stop and there is this customer who wanted a fluid change in his power steering. The company recommended against it because there was a leak, telling him that it might make the leak worse. And it did. And they were topping him off for free for a long time. The general manager bitched and corporate said "The customer is always tight". Well I am here to tell you that is not true. If the customer was always right he would not need you to do WHAT HE CANNOT DO.

But the kid says (and actually he is pretty sharp for his age) that many companies are so afraid of any bad publicity that they will just bend over and take the ass fucking from anyone.

Well homey don't play dat. I had people try to run game on me at my shop and I ran them off with a shotgun. And we did fine. Always made money. If you're straight with me I am straight with you.

 

[Phil Allison]

jurb...@gmail.com wrote:

-------------------------------

"Very nice explanations! "

Yeah Phil beat me to it and probably did a better job, except for
explaining the actual power dissipation of the cap in question.
Really, it is as simple as Ohm's law except you need an accurate
RMS current factor.

** It is not simple to measure or calculate the ACTUAL dissipation - cos ESR varies from sample to sample plus with running temp and age of the cap.



...... Phil

 

[Ian Field]

"Chris" <cbx@noreply.com> wrote in message
newsi6qfn$gsh$31@dont-email.me...

On Sun, 18 Jun 2017 19:35:44 +0000, Jasen Betts wrote:

On 2017-06-18, Chris <cbx@noreply.com> wrote:
Hi all,

What's the deal with this? I read somewhere that a high ripple current
figure for an electrolytic is a bonus; an expensive and sought-after
characteristic. However, I'd always thought ripple was anathema to
PSUs.
Can some expert kindly explain the relationship between ESR, ripple
current, capacitor ageing and whatnot?

It means that it withstands a high ripple current.

What's to "withstand"? Electroytics are designed to smooth that out,
after all.

ESR is an apparent series resistance inside the capacitor. Ripple current is
the capacitor charging and discharging from the rectifier pulses of current
and the load current in between the rectifier current.

The ripple current flows through the apparent series resistance and produces
heat. heat accelerates the processes that cause ESR to increase.

Low ESR is good, but its things like SMPSUs that need the more expensive
parts.

Very often you can improve matters by putting metalized foil or MLCC
capacitors in parallel with electrolytics.

 

[Phil Allison]

Ian Field wrote:

-----------------

The ripple current flows through the apparent series resistance and produces
heat. heat accelerates the processes that cause ESR to increase.

** Fraid it does the opposite.

ESR is almost entirely due to the conductivity of the electrolyte and THAT improves as it get hotter. At max rated temp ( ie 85C or 105C ) the ESR falls by a factor of 4 or 5 compared to room temp.

Very often you can improve matters by putting metalized foil or MLCC
capacitors in parallel with electrolytics.

** No you can't.


..... Phil

 

[Chris]

On Mon, 19 Jun 2017 20:23:36 +0100, Ian Field wrote:

What's to "withstand"? Electroytics are designed to smooth that out,
after all.

ESR is an apparent series resistance inside the capacitor. Ripple
current is the capacitor charging and discharging from the rectifier
pulses of current and the load current in between the rectifier current.

The ripple current flows through the apparent series resistance and
produces heat. heat accelerates the processes that cause ESR to
increase.

Thanks, Ian. I think I've got it now. Great explanation.

Low ESR is good, but its things like SMPSUs that need the more expensive
parts.

Right...so in such an application as SMPSs you would seek caps with the
lowest ESRs and the highest ripple current capability?

Would specifically audio-type electrolytics fit the bill here, I wonder?

Very often you can improve matters by putting metalized foil or MLCC
capacitors in parallel with electrolytics.

What for? Flattening off spikes and transients?

 

[Ian Field]

"Phil Allison" <pallison49@gmail.com> wrote in message
news:69c35e89-f707-4fb9-bf13-f5dc3db1c419@googlegroups.com...

Ian Field wrote:

-----------------


The ripple current flows through the apparent series resistance and
produces
heat. heat accelerates the processes that cause ESR to increase.


** Fraid it does the opposite.

ESR is almost entirely due to the conductivity of the electrolyte and THAT
improves as it get hotter. At max rated temp ( ie 85C or 105C ) the ESR
falls by a factor of 4 or 5 compared to room temp.

Has Australia run out of lithium again?!!!

ESR improves temporarily with temperature rise - heat accelerates the
process of increasing ESR by evaporating the "conductive" electrolyte and/or
forcing it out of the seal.

Very often you can improve matters by putting metalized foil or MLCC
capacitors in parallel with electrolytics.


** No you can't.

Perhaps you should tell the manufacturers who waste millions padding
electrolytics with ceramic capacitors.

 

[whit3rd]

On Tuesday, June 20, 2017 at 10:15:27 AM UTC-7, Chris wrote:

On Mon, 19 Jun 2017 20:23:36 +0100, Ian Field wrote:

What's to "withstand"? Electroytics are designed to smooth that out,
after all.

ESR is an apparent series resistance inside the capacitor.

Low ESR is good, but its things like SMPSUs that need the more expensive
parts.

Right...so in such an application as SMPSs you would seek caps with the
lowest ESRs and the highest ripple current capability?

Well, no. The SMPS has an input filter, at a few hundred volts bias, that
only sees an amp or so, as well as a 3.3V output filter, that sees near a hundred
amps of ripple. If you put the low-ESR cap at the input filter, it just means
that your ON/OFF switch makes a fat spark every time you apply power.
Switch life, and RF radiated interference, are your new problems.

and, if you DON'T put a low-ESR cap at the output filter, the ten milliohms of
ESR, which feeds that hundred amp load, can have up to 1V of effect (i.e.
your regulation suffers).

If the ESR of the output caps and capacitance of the output caps are both
in the 'good enough' range, go on to the next problem. One 10 milliohm
capacitor won't do, but fifteen in parallel is OK. The CPU that takes all
that power, has a dozen power input pins, anyhow: there's wiring resistance
to consider, so a microohm ESR for the capacitor doesn't help much.

 

[Ian Field]

"Chris" <cbx@noreply.com> wrote in message
newsibl0f$j5m$1@dont-email.me...

On Mon, 19 Jun 2017 20:23:36 +0100, Ian Field wrote:

What's to "withstand"? Electroytics are designed to smooth that out,
after all.

ESR is an apparent series resistance inside the capacitor. Ripple
current is the capacitor charging and discharging from the rectifier
pulses of current and the load current in between the rectifier current.

The ripple current flows through the apparent series resistance and
produces heat. heat accelerates the processes that cause ESR to
increase.

Thanks, Ian. I think I've got it now. Great explanation.


Low ESR is good, but its things like SMPSUs that need the more expensive
parts.

Right...so in such an application as SMPSs you would seek caps with the
lowest ESRs and the highest ripple current capability?

Would specifically audio-type electrolytics fit the bill here, I wonder?


Very often you can improve matters by putting metalized foil or MLCC
capacitors in parallel with electrolytics.

What for? Flattening off spikes and transients?

Only partly - MLCC capacitors are among the lowest ESR, but most non
electrolytic are not too bad. They present a lower impedance to fast
transients and take some of the heat off the electrolytic.

Its quite possible that very expensive low ESR electrolytics are being
offered to audiophools - but I wouldn't take their word for it without
reading the data sheet.

 

[Phil Allison]

Ian Field wrote:

----------------------------

The ripple current flows through the apparent series resistance and
produces
heat. heat accelerates the processes that cause ESR to increase.


** Fraid it does the opposite.

ESR is almost entirely due to the conductivity of the electrolyte and THAT
improves as it get hotter. At max rated temp ( ie 85C or 105C ) the ESR
falls by a factor of 4 or 5 compared to room temp.


ESR improves temporarily with temperature rise -

** Bullshit about the "temporarily" part.

It does so for the whole life of the electro cap.

heat accelerates the
process of increasing ESR by evaporating the "conductive" electrolyte and/or
forcing it out of the seal.

** Heat reduces an electro's useful life.

Claiming ESR rises is a red herring.

Very often you can improve matters by putting metalized foil or MLCC
capacitors in parallel with electrolytics.


** No you can't.

Perhaps you should tell the manufacturers who waste millions padding
electrolytics with ceramic capacitors.

** Very few do any such thing and those that do are wasting their money.

Just wanking - like you.


..... Phil

 

[Phil Allison]

Chris wrote:

--------------------

Ian Field wrote:


ESR is an apparent series resistance inside the capacitor. Ripple
current is the capacitor charging and discharging from the rectifier
pulses of current and the load current in between the rectifier current.

The ripple current flows through the apparent series resistance and
produces heat. heat accelerates the processes that cause ESR to
increase.

Thanks, Ian. I think I've got it now. Great explanation.

** Ian is a bullshitting fool and his explanations are full of errors.

Low ESR is good, but its things like SMPSUs that need the more expensive
parts.

Right...so in such an application as SMPSs you would seek caps with the
lowest ESRs and the highest ripple current capability?

** Err --did you read my post on this at all ???

Would specifically audio-type electrolytics fit the bill here, I wonder?

** Keep wondering.

Bloody audiophool.



....... Phil

 

[Phil Allison]

Ian Field wrote:

-------------------------

What for? Flattening off spikes and transients?

Only partly - MLCC capacitors are among the lowest ESR, but most non
electrolytic are not too bad. They present a lower impedance to fast
transients and take some of the heat off the electrolytic.

** Audiophool bollocks.




....... Phil

 

[Phil Allison]

whit3rd wrote:

----------------

Right...so in such an application as SMPSs you would seek caps with the
lowest ESRs and the highest ripple current capability?

Well, no. The SMPS has an input filter, at a few hundred volts bias, that
only sees an amp or so, as well as a 3.3V output filter, that sees near a
hundred amps of ripple.

** Really, what PSU is that?

SMPSs come in all sizes.

If you put the low-ESR cap at the input filter, it just means
that your ON/OFF switch makes a fat spark every time you apply power.

** Horse poo.

SMPSs always have an inrush surge limiter fitted.



...... Phil

 

"> The ripple current flows through the apparent series resistance and produces
heat. heat accelerates the processes that cause ESR to increase.

** Fraid it does the opposite."

That depends on the exact parameter you are attacking.

It is true that a lytic will have higher ESR at lower temperatures, but when exposed over time to higher temperatures, especially cycles, their average ESR will go up. While this is still dependant on temperature the basic factor of it is worse, higher ESR.

Leiberman was up here like last year with a chart he made with a pot of water, thermometer and ESR meter. I would almost like to see how those same caps fare after being in service for a couple of years. If he still has the time to burn of course.

I would not buy an ESR meter, I can measure that with a scope or a few other means. But after being in service they deteriorate and we all know that. But if they are not leaking fluid out or anything, what is causing it ?

The only explanation is that the electrolyte is losing its electrolytic properties. There was no leak, the plates did not change, the application of the electrodes to the plates did not change, or did they ? You know a bit more about the construction of these things so you speculate on that. However I think that a problem with the connections would cause higher ESL, moreso than ESR. The only thing left is the electrolyte. And I remember the almost wars over their formulae.

The leaky ones were a different story, they leaked all over the boards in alot of shit. I got to the point where I did not replace them, they already done leaked. I washed the shit out of the board and was usually done with it. The thing is seven years old and this is fixed now, see you in seven years. The only real problem is when that shit ate the copper right off the board. But that is why I got the big bucks.

 

[Phil Allison]

jurb...@gmail.com wrote:

--------------------------------

"> The ripple current flows through the apparent series resistance
and produces heat. heat accelerates the processes that cause
ESR to increase.


** Fraid it does the opposite."

That depends on the exact parameter you are attacking.

** That idiotic post has been thoroughly answered - fuckhead.

It is true that a lytic will have higher ESR at lower temperatures,
but when exposed over time to higher temperatures, especially cycles,
their average ESR will go up.

** Utter FUCKING BULLSHIT !!!!!!!!!!!!!!

Jerb is a congenital, TROLLING LIAR !!!!!!!

I would not buy an ESR meter,

** And I would not sell you one - cos YOU are a FUCKING IDIOT !!

A six toed, dribbling, banjo plucking, pig fucking, toothless retard.

And they are your best qualities.







..... Phil