Subject: Re: 2.5kW-3kW-SMPS-(cheap)-suggestions?
Date: Mon, 16 Dec 2002 22:55:01 +0000 (UTC)
NNTP-Posting-Date: Mon, 16 Dec 2002 22:55:01 +0000 (UTC)
User-Agent: tin/1.5.14-20020926 ("Soil") (UNIX) (Linux/2.4.19 (i686))
John Jardine wrote:
> I've little idea of SMPS beyond a 200W DC step-up, so an AC-DC 2.5 to 3kW
> step-down seems an out of reach, nightmare.
> The more I look into it the more I seem either spoiled for choice, or have
> no choice at all. I wonder if someone familiar with the black art of these
> things can throw some crumbs off their table sufficient to allow me some
> kind of compass direction to point at?.
> The suggestion is for a piece of portable kit that will be powered from an
> on-site 110Vac generator (95V-140V building site type!) and will give as o/p
> (unsorted yet) 40-50V DC (say 55amps max). The power will be dumped into a
> resistive heating element (one shot) for up to maybe 30 minutes a time.
> Operating duty cycle about 60%. ('tool' rating).
I wonder if you'r going too complex.
Take a few uf of motor run capacitors (well, low ESR anyway), attatch across
Now attatch a bridge to give you DC.
Now put a biggish FET between that DC and the load, and PWM it so that
the overall power factor comes back to a resistive load.
Yes, the waveform across the resistive load isn't DC, but do you care?
No magnetics or stability problems, ...
http://inquisitor.i.am/ | mailto:firstname.lastname@example.org | Ian Stirling.
The fight between good and evil, an epic battle. Darth vader and Luke,
suddenly in the middle of the fight, Darth pulls Luke to him, and whispers
"I know what you'r getting for christmas!" Luke exclaims "But how ??!?"
"It's true Luke, I know what you'r getting for christmas" Luke tries to ignore
this, but wrenches himself free, yelling "How could you know this?",
Vader replies "I felt your presents" -- The Chris Evans breakfast show ca. 94