Re: Using an AC-to-AC wall wart transformer/adapter in reverse
- From: JosephKK <quiettechblue@xxxxxxxxx>
- Date: Mon, 09 Feb 2009 22:43:25 -0800
On Mon, 09 Feb 2009 13:09:07 -0500, Ben Bradley
<ben_nospam_bradley@xxxxxxxxxxxxxxx> wrote:
On Sun, 08 Feb 2009 15:55:17 +1100, Sylvia Else
<sylvia@xxxxxxxxxxxxxxxxxxx> wrote:
Eeyore wrote:
Sylvia Else wrote:
Since when is the output voltage of a simple transformer a significant
function of load?
This makes me wonder if your experience is with substation
transformers or pole pigs or what.
Since Michael Faraday ? first wound one maybe ?
Graham
The voltage on the primary is determined by the rate of change of flux,
but also has to equal the supply voltage.
Since that flux is linked to the secondary, the secondary sees the same
rate of change of flux, with the voltage on the secondary being related
to the voltage on the primary just by the number of turns.
In the absence of hysteresis losses on the core, flux leakage, and
resistance, this relationship remains true regardless of load.
In the absence of any practical real-life limitations, I am
perfect. :-)
There are of course such losses, but the transformer is designed to
minimise them. The 25% loss suggested by Phil seems extreme.
Phil may even be understating it (which is unusual for Phil).
Wallwarts are made cheap. Using smaller gauge wire and crappy core
causes lower efficiency at rated load (thus it runs warmer and costs
the consumer more electricity to run it), higher no-load voltage and
other bad engineering crap. Actually, I also understand the core is
operated at or near saturation (because it takes fewer turns this way,
thus saving copper wire), which may actually help regulation, but the
wire resistance is so high it hardly makes a difference.
Wallwarts are designed to minimize three things: cost, cost, and
cost.
Of course all that's obsolete now that there are off-line switching
supplies made smaller and cheaper than walwart transformers.
Perhaps the Japanese, and now Chinese, learned as much from Muntz
as they ever did from Deming. It's amazing the USA has survived this
long, we keep giving away all our good ideas.
Speaking of Demming, not only did we give them the best we had, but
American industrialists persisted in refusing to implement those
techniques ourselves for decades.
.
Sylvia.
- References:
- Using an AC-to-AC wall wart transformer/adapter in reverse
- From: Matt
- Re: Using an AC-to-AC wall wart transformer/adapter in reverse
- From: Phil Allison
- Re: Using an AC-to-AC wall wart transformer/adapter in reverse
- From: Sylvia Else
- Re: Using an AC-to-AC wall wart transformer/adapter in reverse
- From: Eeyore
- Re: Using an AC-to-AC wall wart transformer/adapter in reverse
- From: Sylvia Else
- Re: Using an AC-to-AC wall wart transformer/adapter in reverse
- From: Ben Bradley
- Using an AC-to-AC wall wart transformer/adapter in reverse
- Prev by Date: Re: Conclusive physical evidence for AWG?
- Next by Date: Re: How many steps in a variac
- Previous by thread: Re: Using an AC-to-AC wall wart transformer/adapter in reverse
- Next by thread: Re: Using an AC-to-AC wall wart transformer/adapter in reverse
- Index(es):
Relevant Pages
|
