Why do capacitors short out at high frequencies?

No offense, but this sounds a bit fishy. Have you got a reliable cite for that? Every spec of a cap can be tested accurately, and even minimal AQL testing will reveal such a basic design flaw. I find it hard to believe that any significant cap manufacturer would fail to thoroughly test a new cap design, especially those operatiing under ISO-9000 guidlines.

Give me a couple minutes…

Ask and you shall receive…

IEEE Spectrum Article

From the article…

What is up with the hamsters today?

Sounds like a lot of finger-pointing and excuse-making to me. Certainly someone screwed up, but I don’t think we’ll ever know the real truth in a case like this.

In terms of its capacity, a hamster is really just a micro-ferret. To get the board up to speed really requires a full ferret or more. :smiley:

Not necessarily. If the formula was wrong then I’m guessing the capacitors would only fail under certain conditions over time. “Conditions” may include high ambient temperature and/or high ripple current. This defect is easily identified when using accelerating life testing, environmental cycling, etc., but these are performed during product development, not on the assembly line.

ISO-9000 guidelines don’t say anything about testing stuff. It mostly just means you have a process and you follow the process. You can have crappy processes and get certified.

Good catch, gazpacho. ISO-9001 is a total joke. But I guess that’s better left for IMHO…

Sort of. But the processes do get evaluated as well. I was an ISO auditor for a former employer, a transformer manufacturer. I got to spend three days at this cool (read “boring”) ISO-9000 training class.

This is just wrong. The formula is X[sub]c[/sub]=1/(j.w.C), as N9IWP originally said. There’s no square root in the formula.

didn’t think there was a square root, but wasn’t sure.
(Hangs head in shame).


You’re correct that there is no square root (thanks for making me drag out my engineer’s reference), however, if you want to get technical, the correct formula is actually X[sub]C[/sub]=1/(**-**jwC). That minus sign is important if you’re going to factor in the imaginary component.

That’s wrong, too. The correct formula is X[sub]C[/sub]=1/(jwC). If you wanted to explicity include the minus sign, you’d write X[sub]C[/sub]=**-**j/(wC).

Desmostylus is correct; the complex impedance for an ideal capacitor is Z(jw) = 1/(jwC). The magnitude of the impedance is 1/(wC).

I can see I need to review my formulae. It’s been a while since I’ve used this stuff in practice. :smack: