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From: "Kevin White"
References: <0001HW.B9DF7C5F00256614162B2870@news.covad.net> <firstname.lastname@example.org>
Subject: Re: Boosting output from 120V inverter
X-Newsreader: Microsoft Outlook Express 6.00.2800.1106
NNTP-Posting-Date: Sun, 27 Oct 2002 03:04:00 GMT
Organization: AT&T Broadband
Date: Sun, 27 Oct 2002 03:04:00 GMT
Well actually, increasing the load will take the transformer out of
The current in the secondary opposes the magentic field created by the
primary. (assuming a forward converter as I believe they usually are). If
there is feedback that increases the drive when the output drops then yes it
may put the transformer into saturation. But that is usually determined by
the input voltage.
This is assuming a system with a separate oscillator and output stage, the
traditional push-pull self-timed inverter always runs the transformer to
saturation anyway as part of its normal operation.
You may not be able to get much more out of the transformer because the
resistance and leakage inductance may be limiting the output power.
"Bob Wilson" wrote in message
> In article ,
> email@example.com says...
> >"Bevan Weiss" wrote in message
> >> It's not that simple unfortuneately...
> >> The transformer itself probably wont be rated that much above what the
> >> entire inverter is rated at. So just replacing the MOSFET's wouldn't
> >> trick, you'd have to replace the transformer as well, and the
> >> almost the entire cost of an inverter, apart from design.
> >> "DaveC" wrote in message
> >> news:0001HW.B9DF7C5F00256614162B2870@news.covad.net...
> >> > 200W inverter needs to run a bit more power. I know how cheap these
> >> > are, but I get my kicks from using and/or modifying what I have and
> >> getting
> >> > the experience of electronics theory/application.
> >> >
> >> > How should I go about matching up a higher-amperage MOSFET to replace
> >> > ones there? Same g-d and g-s voltages? Higher d current? Pin
> >> configuration,
> >> > of course. What are the critical specs I should focus on when looking
> >> an
> >> > upgrade?
> >> >
> >> > The MOSFETS that switch the output are not heatsinked very well, and
> >> is
> >> > room for a small cooling fan.
> >> > --
> >> > Note that my return address is corrupted in an attempt to reduce
> >> you
> >> > choose to e-mail me, please correct my address as described below.
> >> >
> >> > Thanks,
> >> > Dave
> >I think it could work actually, with a fan. Transformers will handle
> >much more power when fan cooled. So I'd put as powerful a fan in there
> >as you can squeeze, uprate your fets, and watch the TF temp to see
> >what it'll manage continuous. Hopefully you'll get a significant
> Baloney! The transformers used in the typical low cost inverter (and I can
> speak from experience here) are designed to run close to their saturation
> limits. Push them harder (even if you cool them) and they start going into
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