DC Power supply question...duh...

From: Aaron Christopher Finney <af-list_at_lafleur.wfi-inc.com>
Date: Thu Jul 1 16:03:05 1999

Thanks, everyone who answered. I think I'm going to spring for another PS
that I know is rated for the full 12 amps. Just out of curiosity, what
could conceivably happen if I ran it at 12 amps and it couldn't handle the
load? By the way, it is indeed an inexpensive, linear type...

Thanks again,

Aaron

On Thu, 1 Jul 1999, Tony Duell wrote:

> >
> > I am risking the effects of that famous quote, "Better to be thought a
> > fool..."
> >
> > I have a 15V DC powersupply that has no other rating on its sticker than
> > 180 watts. Now, with my [extremely] limited knowledge, I did the simple
> > math and worked out that I could safely pull 12 amps out of this
> > PS...am I right? Does it really work this way?
>
> In theory, yes.
>
> DC power = I.V. So 180W at 15V is, indeed, 12A.
>
> However, that is taking the '180W' to be the output power of the supply.
> In many cases, the 180W is the maximum power it will consume from the
> mains. And as power supplies are not 100% efficient, you don't get out
> all the power you put in. In fact, the efficiency might only be 50%
> (particularly if it's a linear PSU), so you could only draw 6A from it.
>
> I'd probably not take more than that from it, unless I _knew_ it was
> designed to stand it.
>
> -tony
>
Received on Thu Jul 01 1999 - 16:03:05 BST