Ian,
You have done any work on an SMPS at these high power levels (1KVA to 10KVA)
?
I'd would be _very_ interested in such a design :)
Alex, N2NNU
===================================
If we can accept the notion that GUNS are
the killers and not the people, why is it that
we can not accept the idea that CARS are
the speeders and not the drivers?
Alex, trying to understand the world around.
==================================.
----- Original Message -----
From: "Ian White, G3SEK" <G3SEK@ifwtech.com>
To: <amps@contesting.com>
Sent: Saturday, December 15, 2001 10:00 AM
Subject: Re: [AMPS] Transformer Current ratings
>
> Jerry Flanders wrote:
> >
> >For "ordinary" old power transformers:
> >
> >Is there a rule of thumb to help estimate transformer KVA capacity from
> >the iron (or total) weight? If not, why?
> >
> >Prior to hypersil, weren't most transformers made from similar iron in
> >similar configuration? If so, wouldn't capacity be directly related to
> >core weight?
>
> Only indirectly. Weight is a rough indication of core cross-section,
> which is important but still only one factor in the transformer's
> overall performance.
>
> The rule of thumb was "Size of a six-pack = 500 watts, size of a 12-pack
> = 1500 watts, too heavy to lift = 2500+ watts!" This of course is very
> variable, and older transformers tend to be bigger and heavier for their
> power rating than modern ones.
>
> However, I have been bitten several times in the past by building a
> whole PSU - or even a whole amp - around a transformer that passed the
> rule-of-thumb weight test but was quite unsuitable.
>
> A *much* better way is to measure the winding voltages and resistances
> and look at the electrical performance. Rich gives some useful
> electrical rules of thumb, but before you commit to building a whole
> power supply around a particular transformer, you'd do well to run it
> through the 'PSU Designer' software.
>
> 'PSU Designer' is Windows freeware from an audio firm called Duncan
> Amplification and it's an easy way to put some real 21st-century
> accuracy into PSU design. Duncan's amps use relatively small PSUs by our
> standards, but the software works just fine for big PSUs too.
>
> I wrote a short article on it in my monthly magazine column, and there
> are links from: http://www.ifwtech.com/g3sek/in-prac/ Slide down to
> August 2001, where there are links to the download site and some extra
> files to download.
>
> The extra files relevant to AMPS are the circuit files '3kV Bridge.psu'
> and '3kV Doubler.psu', and you'll also need the expanded RECTIFIERS.TXT
> file which contains a high-voltage rectifier.
>
> The two .psu files are a basis for modeling normal high voltage
> supplies. Double-click on any item in the schematic to alter its
> properties, and then click Simulate to get a simulation over a chosen
> time period. You can change the load current by altering the current
> sink connected to the output.
>
> Then click various items on the form below to see graphs over time. The
> most interesting item is probably V(C1) - the output voltage.
>
> As you get further into using PSU Designer, check the Help files for
> more information.
>
> A note about transformer modeling: PSU Designer only lets you model the
> secondary resistance of the transformer. You can include the effects of
> (primary + mains supply) resistance by multiplying those values by the
> square of the step-up turns ratio and adding the answer to the secondary
> resistance. There's more information if you double-click the transformer
> symbol, and then choose Help.
>
> This really is a great program! It takes some practice, but I wouldn't
> ever build another PSU without running the components through PSU
> Designer.
>
> Coming back to Jerry's original question about current ratings, if the
> winding resistances are low enough to give good voltage regulation at
> the currents you want, you pretty much have your answer about current
> ratings too.
>
> --
> 73 from Ian G3SEK Editor, 'The VHF/UHF DX Book'
> 'In Practice' columnist for RadCom (RSGB)
> http://www.ifwtech.com/g3sek
>
> --
> FAQ on WWW: http://www.contesting.com/FAQ/amps
> Submissions: amps@contesting.com
> Administrative requests: amps-REQUEST@contesting.com
> Problems: owner-amps@contesting.com
>
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