Hello,
Long post, but please only skim read and I beg you to shovel any answer you think may have any relevance whatsoever (even if it doesn’t) , to this horrendous subject of pinning down the actual lifetime of radial leaded electrolytic capacitors………
Our investors want us to write them a report on the lifetime of “Wet” Aluminium Electrolytic Capacitors in our product. (60W offline flyback, 110-265VAC input)
The electroytic capacitor we are using is the Acon KL series 400V, 100uF one. (as attached)
This is the capacitor that our Chinese designers put in our product. (Post rectifier capacitor)
The Chinese designers sent us the attached lifetime calculation for this capacitor.
The strange thing is, in this formula, if one decreases the ripple current value flowing in the capacitor, then the lifetime decreases!!!....
(This is from one of the bigegst SMPS designers in China...they make SMPS for most of the western world.)
….This can’t be right, does anyone know what’s gone wrong here? And is there any other formulae for radial leaded electrolytic capacitors lifetime?
As you can see, the Chinese capacitor lifetime equation lists a parameter called “delta(Tj0)”…
This parameter is the “internal temperature rise when rated ripple current is applied”.
Strangely, they don’t tell us what this value [“delta(Tj0)”] is for the Acon KL series capacitor…..instead, their lifetime equation simply gives “delta(Tj0)” values for the Rubycon USR, USC & USG series capacitors. –But that’s not what we are using, so why do they state it?
Also, another parameter used in the attached lifetime equation is called “alpha”. It is the “ratio of the case top and core of the capacitor element”. From the attached lifetime exerpt, you can see that the lower the diameter of the capacitor body, the greater the temperature of the capacitor case gets. Is this typical for other electrolytic capacitors too?...it doesn’t seem to make sense…..because surely the deciding factor is how long the capacitor body is?....that is, longer body capacitors would run hotter as its further from the internals to the base…the base being where most heat transfers out of the capacitor?
Anyway, why does our Chinese designers lifetime equation give a lower lifetime when the capacitor has less ripple current in it? Have I missed something?
Also, why does no radial electrolytic capacitor manufacturer give thermal resistance values from internal core to the case for their capacitors?..it is impossible to actually do a lifetime calculation without this information.
Long post, but please only skim read and I beg you to shovel any answer you think may have any relevance whatsoever (even if it doesn’t) , to this horrendous subject of pinning down the actual lifetime of radial leaded electrolytic capacitors………
Our investors want us to write them a report on the lifetime of “Wet” Aluminium Electrolytic Capacitors in our product. (60W offline flyback, 110-265VAC input)
The electroytic capacitor we are using is the Acon KL series 400V, 100uF one. (as attached)
This is the capacitor that our Chinese designers put in our product. (Post rectifier capacitor)
The Chinese designers sent us the attached lifetime calculation for this capacitor.
The strange thing is, in this formula, if one decreases the ripple current value flowing in the capacitor, then the lifetime decreases!!!....
(This is from one of the bigegst SMPS designers in China...they make SMPS for most of the western world.)
….This can’t be right, does anyone know what’s gone wrong here? And is there any other formulae for radial leaded electrolytic capacitors lifetime?
As you can see, the Chinese capacitor lifetime equation lists a parameter called “delta(Tj0)”…
This parameter is the “internal temperature rise when rated ripple current is applied”.
Strangely, they don’t tell us what this value [“delta(Tj0)”] is for the Acon KL series capacitor…..instead, their lifetime equation simply gives “delta(Tj0)” values for the Rubycon USR, USC & USG series capacitors. –But that’s not what we are using, so why do they state it?
Also, another parameter used in the attached lifetime equation is called “alpha”. It is the “ratio of the case top and core of the capacitor element”. From the attached lifetime exerpt, you can see that the lower the diameter of the capacitor body, the greater the temperature of the capacitor case gets. Is this typical for other electrolytic capacitors too?...it doesn’t seem to make sense…..because surely the deciding factor is how long the capacitor body is?....that is, longer body capacitors would run hotter as its further from the internals to the base…the base being where most heat transfers out of the capacitor?
Anyway, why does our Chinese designers lifetime equation give a lower lifetime when the capacitor has less ripple current in it? Have I missed something?
Also, why does no radial electrolytic capacitor manufacturer give thermal resistance values from internal core to the case for their capacitors?..it is impossible to actually do a lifetime calculation without this information.