What current rating for a cap?

[chico1st]

Hi there when I am selecting a current rating on a replacement cap how do I determine the current rating?

So far for any fixes I just choose the highest value that fits but how do you go about deciding if they are high enough?

Same goes for fuses.

Without having a schematic some of these things are hard.

[PlainBill]

Re: What current rating for a cap?

Hi there when I am selecting a current rating on a replacement cap how do I determine the current rating?

So far for any fixes I just choose the highest value that fits but how do you go about deciding if they are high enough?

Same goes for fuses.

Without having a schematic some of these things are hard.

The best approach is to determine the current rating of the original cap and try to match it. Most capacitors have a two or three character series designation printed near the temperature rating. Look that up and you can determine the specs.

Here's an example. I just pulled a CapXon 1000uF 25V cap out of the bag of junk caps. On the opposite side it says KF 105°C. Googling CapXon KF series I find that it is rated for a ripple current of 1650 ma, and an impedance of .045ohms. A quick search of Digikey's site shows that the Panasonic FC series and the United Chemi-Con LXZ and LXY series would be a good match.

PlainBill

[PCBONEZ]

Re: What current rating for a cap?

Hi there when I am selecting a current rating on a replacement cap how do I determine the current rating?

So far for any fixes I just choose the highest value that fits but how do you go about deciding if they are high enough?

Same goes for fuses.

Without having a schematic some of these things are hard.

You look in the data sheet, but caps have more than one current rating.
.
For DC you look at Leakage Current.
.
For AC you look at Ripple Current but it will be given at some specific frequency. [Typically 100Hz, 120Hz or 100kHz.]
There will be conversion factors in most data sheets to find the current rating at other frequencies.
.

[chico1st]

Re: What current rating for a cap?

OK I understand the ripple current etc measurements at a high level, but on this data sheet for capxon KF...

the ripple current is measured in SV? what the heck is that?
I would assume that it reads as 10V 2200uF cap is 1.65 A ripple? is that right?

[PCBONEZ]

Re: What current rating for a cap?

Crap brands often have screwy data sheets and CapXon is no exception.
.
SV is for Surge Voltage. Not generally shown in data sheets.
Use the value for WV - That's the industry standard rating.
.
Yes 1650 mA = 1.6 A
.

[PCBONEZ]

Re: What current rating for a cap?

Also realize that the voltage rating is a total - as in Ripple Volts + DC Volts.
.