Ripple factor

[dbanner]

Ripple factor? Electrolytic capacitors are different sizes even though they are rated as same value both in capacitance and voltage. Some are miniature compared to others but are rated at same voltage(and capacitance)
So what is ripple factor and how do you know if you can use smaller caps without getting the magic smoke or a short lifespan.

[kt315]

there is some history about electrolitics in russian environment. chinese did stole chemical recipe from japanese. but japanese changed the recipe seen problem.
so chinese does the electrolitics using first one and can not stole moded. thats why chinese caps are still bad.

[Andi68]

https://en.wikipedia.org/wiki/Ripple_(electrical)

[waltr]

Ripple factor? Electrolytic capacitors are different sizes even though they are rated as same value both in capacitance and voltage. Some are miniature compared to others but are rated at same voltage(and capacitance)
So what is ripple factor and how do you know if you can use smaller caps without getting the magic smoke or a short lifespan.

Ripple is 'AC' on top of the DC. Typical is the old AC mains step-down x-former and rectifier with a single diode (Half-wave rectification). Look this up or better build this and look at the diode output on an O'scope.
This is technically DC since the polarity does not change but the Voltage does go from 0V to max V at the frequency on the AC mains. This is 'ripple'.

Now a cap is placed across to 'smooth' this ripple to closer to a non-varying DC voltage. The cap is being Charged and Discharged at the Main frequency. This cap must have a high ripple rating.

Inside a Cap are parallel plates separated by an electrolyte and insulator. A charge on the plates (one positive and one negative) create an attractive force and the plates try to pull closer to each other. When the Voltage lowers the charge and hence Force decreases and the attraction decreases. The plate then move away from each other. Now have the plate move toward and away at the AC frequency. This mechanical motion creates heat and stress. A cap not designed for this (low or no Ripple rating) will fail. One failure mode is the plates 'wear through' the electrolyte/insulate and the plates touch creating a Short.

Does this answer your question (it is a good question)?

[Andi68]

A good explanation

[dbanner]

Ripple is 'AC' on top of the DC. Typical is the old AC mains step-down x-former and rectifier with a single diode (Half-wave rectification). Look this up or better build this and look at the diode output on an O'scope.
This is technically DC since the polarity does not change but the Voltage does go from 0V to max V at the frequency on the AC mains. This is 'ripple'.

Now a cap is placed across to 'smooth' this ripple to closer to a non-varying DC voltage. The cap is being Charged and Discharged at the Main frequency. This cap must have a high ripple rating.

Inside a Cap are parallel plates separated by an electrolyte and insulator. A charge on the plates (one positive and one negative) create an attractive force and the plates try to pull closer to each other. When the Voltage lowers the charge and hence Force decreases and the attraction decreases. The plate then move away from each other. Now have the plate move toward and away at the AC frequency. This mechanical motion creates heat and stress. A cap not designed for this (low or no Ripple rating) will fail. One failure mode is the plates 'wear through' the electrolyte/insulate and the plates touch creating a Short.

Does this answer your question (it is a good question)?

Thanks for the answer, now I see a little clearer. so this ripple rating is printed on side some caps? I never really paid attention to all the specs printed on cap.
So high current plus ripple can bring the magic smoke if no using properly rated cap?
Now I see why there are always typical swollen caps in power supply of many devices. They eventually break down because of tiny ripple and high current.
Especially if they are Chinese brand.

[waltr]

I have never seen the Ripple rating printed on caps. It is only in the data sheets and if the data sheet does not list a ripple rating then that cap is NOT for high ripple applications.

Yep, that is why PS caps commonly fail and many times spectacularly.

[dbanner]

I have never seen the Ripple rating printed on caps. It is only in the data sheets and if the data sheet does not list a ripple rating then that cap is NOT for high ripple applications.

Yep, that is why PS caps commonly fail and many times spectacularly.

Thanks.
This is all very good to know.