Capacitor voltage ratings

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exxos
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Capacitor voltage ratings

Post by exxos » Fri Jul 06, 2018 7:41 pm

I bought a stack of ceramic capacitors ages ago, surplus stuff. They were rated at 6.3V. Though I just hooked up one to my power supply and ran it at 50VDC and it did not fail. Even shorted it out times and then measured the value again fine. So I wonder if they just put 6.3V because they did not know the voltage..

On the other hand, I really have wondered if manufacturers are just charging more for higher rated voltages when they are exactly the same part as the lower voltage ones..

Take for example

6.3V £2.12p
https://www.mouser.co.uk/ProductDetail/ ... fZPonTM%3d

10V £2.42
https://www.mouser.co.uk/ProductDetail/ ... N1Qn2VI%3d

Then we get onto stacked caps..

16V £3.46
https://www.mouser.co.uk/ProductDetail/ ... YelHGS4%3d

Then other brands...

25V £7.24
https://www.mouser.co.uk/ProductDetail/ ... 4elw%3d%3d


Actually using such capacitors in my new power supply design.. Though as I need about 25VDC for the main input capacitors, I'm using the lower value.

But really, as anyone seen any information about all this anywhere ? I think manufacturers do do these tricks..

Though I don't really get how a supposed 6.3V , and run at 50VDC without blowing it up.. Course is possible these caps are actually higher voltage than the surplus place had them listed at.... Or it is possible there manufacturers just do a huge run up capacitors, or the same spec, and just list them at various prices when possibly they all could be much higher voltages than they quote..
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Re: Capacitor voltage ratings

Post by exxos » Fri Jul 06, 2018 7:57 pm

Why are there no flames :(

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stephen_usher
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Re: Capacitor voltage ratings

Post by stephen_usher » Fri Jul 06, 2018 8:00 pm

Possibly a result of batch testing?

i.e. the lower rated ones are either not tested or the random test sample failed the higher voltage? Maybe all the higher voltage ones are tested and hence cost more in production time?
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Re: Capacitor voltage ratings

Post by exxos » Fri Jul 06, 2018 8:11 pm

stephen_usher wrote:
Fri Jul 06, 2018 8:00 pm
Possibly a result of batch testing?

i.e. the lower rated ones are either not tested or the random test sample failed the higher voltage? Maybe all the higher voltage ones are tested and hence cost more in production time?
I did wonder about batch testing.. Though if these caps are able to run at much higher voltages, why do manufacturers simply not sell them in the first place :roll:

My test probably sux, it could well need high-frequency rapid charging and discharging at the high voltages to test. Though I do not know how manufacturers test this in the first place.. Or if they even do.

It could be that 6.3V simply not tested like you suggest. Though 10V to be the highest voltage rating anyway... That's a long way off from 100V still.
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Re: Capacitor voltage ratings

Post by Neffers » Fri Jul 06, 2018 9:38 pm

Could frequency be a part of it? As in charge and discharge frequency messing with the dielectric over time if the rated voltage is exceeded for prolonged periods at the limit of its designed abilities? And getting bum raped for the privilege of testing.
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Re: Capacitor voltage ratings

Post by exxos » Fri Jul 06, 2018 10:02 pm

Neffers wrote:
Fri Jul 06, 2018 9:38 pm
Could frequency be a part of it? As in charge and discharge frequency messing with the dielectric over time if the rated voltage is exceeded for prolonged periods at the limit of its designed abilities? And getting bum raped for the privilege of testing.
Possibly yes. Though in my case, they are only on the rectifier output, so 100hz stuff.
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Re: Capacitor voltage ratings

Post by Neffers » Fri Jul 06, 2018 10:20 pm

The designation might also be a reflection of how they deal with (as in oppose) AC, reactance, where as your test is just applying DC it's probs just sat there saturated, nothing to do but get a lil bit warm. I really dunno what I'm talking about, I just have a few little bits of crappy logic in my head that occasionally spews out lol.

Edit, also painkillers, get a bit chatty when chewing codiene. Sigh.
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