From: firstname.lastname@example.org (Bob Wilson)
Subject: Re: Boosting output from 120V inverter
Date: Sun, 27 Oct 2002 02:25:46 -0000
Organization: Your Organization
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References: <0001HW.B9DF7C5F00256614162B2870@news.covad.net> <email@example.com> <0001HW.B9DFECA2002E26AD162B2870@news.covad.net>
In article <0001HW.B9DFECA2002E26AD162B2870@news.covad.net>,
>On Fri, 25 Oct 2002 23:03:30 -0700, Bevan Weiss wrote
>(in message <firstname.lastname@example.org>):
>> 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 do
>> trick, you'd have to replace the transformer as well, and the transformer
>> almost the entire cost of an inverter, apart from design.
>Can I gain any increase by properly heatsinking the existing MOSFETs and
>adding a cooling fan? The 2SK1221 is rated at 250V 10A 80W. My
>is that it will handle most of this if kept cool, and less when hot.
You're not listening to the man! It is totally pointless to increase the
current through the primary drive FETs, if the transformer they feed
saturates (and therefore blows up these same FETs!).
>According to the data sheet, power handling capability of this device is
>80W at 25oC and derated - pretty much linearly - down to zero W at 100oC.
>At about 50oC it can handle 50W, which seems like a reasonable temp to keep
>it. But in any case, I think that cooling it as much as possible could only
How do you think cooling is going to help? If all it does is to allow an
increase in primary (FET) current, then we're back to the same problem
again, namely that this increased power, when fed to the transformer(s) will
cause them to saturate and destroy the FETs.
Unless you understand the principles of high frequency transformer design,
and can redesign for higher power throuput, you should forget about the
entire thing. It ain't gonna fly.