[Lowfer] Big Switching HV Power supply - Part II

[W5JGV]

> It is my view as a long-time tinkerer and hands-on advocate
> that projects and descriptions such as this are our greatest
> asset in inspiring, attracting, and recruiting others
> (especially from new generations) to these fields of
> interest. Well done and keep the reports coming. :)

Thanks,

I enjoy writing up my projects, and just wish I had more time to do it.
I like to think that I may help someone else out with a problem or
inspire them to try something new themselves.  I find that I learn a lot
when I really dig in to something like this.  If nothing else, it keeps
my brain cells active!

> I am personally intrigued with this project having lifted and
> carried a very heavy RF power amplifier with a roughly 2kW
> linear power supply (ouch!). Perhaps there's a switcher in my future.

Lets see... the PS for my old 4-1000A AM rig was housed in a half-rack,
and took two people to grunt it up the stairs.  The plate xfmr weighed
about 75 pounds alone.  This supply may weigh in at about 10 pounds or
so when completed. :)

> You note in your update that the two-section TV flyback
> transformers had too small cores to handle the power. Would
> it have been possible or practical to use the cores as pairs
> (for example, side-by-side) and pass the windings around both
> cores to increase the power handling?

The TV flyback cores started off as two "C" shaped cores, placed
pole-to-pole to form a square.  I then took another identical pair of
"C" cores and glued them side by side against the first set, so that I
had a double thickness of ferrite core.

That core handled 500 watts no sweat, and 1 KW intermittently, but 30
minutes at a KW made it get pretty hot.  I could have raised the
switching frequency from 40 KHz to 80 or 90 KHz, but the core losses
were excessive at that frequency.  I think the core materiel was chosen
for a lower frequency, which is reasonable, considering their previous
use in TV output transformers.

73,

Ralph   W5JGV - WC2XSR/13

http://www.emachine.com