Corsair PSU question

[Rifter]

My 850TX seems to be self powered. The other day i turned my computer off to clean it, this was after some heavy gaming so it was warmed up pretty good. I unplugged all the wires and took off the side panel. My PSU fan was still spinning, which is fine im assuming it has a thermal sensor and wanted the PSU to be down to a certan temp even if off. The problem was it WAS NOT PLUGGED INTO THE WALL. So i figued great its got some energy in the caps and will stop withing 30 seconds and i can clean it, wrong it spun the fan for 7 min with no power, is that normal?

 

[qazwsxokmijn]

Ghost!!

 

[v8envy]

I think we have the first documented case of a > 100% efficient power supply.

But yeah, you can store enough energy to kill you in some of those monster capacitors. Spinning a fan for a few hours should be no sweat.

 

[Stefan Payne]

Depending on the fan it may happen but not for 7minutes...

 

[Tsavo]

I think we have the first documented case of a > 100% efficient power supply.

But yeah, you can store enough energy to kill you in some of those monster capacitors. Spinning a fan for a few hours should be no sweat.

110% efficient...sell it on Ebay for $10,000,000.00

 

[Rifter]

Yeah i guess caps holding power is good but i didnt expect that long, next time i clean my PC ill have to let it cool down first.

 

[johnnydrinkawater]

There are usually two 330uF caps in there, in parallel, they are 660uF:

time constant = R x C = R x 0.000660

The time constant (according to wiki) is the time it takes a cap to discharge to about 36% of it's fully charged state.

Let's assume it took 7 minutes (420 sec) for the cap to run out of sufficient power at 36% (this means that the fan requires at least ~4.5V from the caps to register any motion and that the fully charged value of the caps is 12V).

Then,

time constant = 420 sec = R x 0.000660

That means R = ~650k ohms is in series with the caps.

The point is to verify that this value is not out of the question, from a general point of view. However, I don't know what typical values are for PSU design. Of course, being a larger PSU, there may be more large caps in it, thus making the resistance even more typical.

Thanks for reading, I'll take a cookie :awe:

This was more for my entertainment than anything else...