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From: firstname.lastname@example.org (N. Thornton)
Subject: Re: Boosting output from 120V inverter
Date: 28 Oct 2002 13:12:00 -0800
NNTP-Posting-Date: 28 Oct 2002 21:12:00 GMT
>A lot of those transformers are varnish or epoxy impregnated and the
>will not circulate freely.
Well, I don't seriously suggest an oil slick, but if you do want to
try it, it will still work anyway, since the biggest heat flow barrier
is still the transformer to air interface.
>Big UPSes are available cheaply at hamfests. Why go through all this
>and boost a tiny one?
Adding a fan... its not much, and it can uprate the OP's invertor.
Sounds OK to me. Also the OP probably _wants_ to do it, see what they
can achieve. And I bet fitting a fan would be quicker than going to a
hamsterfest. And far cheaper FWIW. I like a challenge anyway.
>>Youve also got the iron core which is
>>intermediate in conduction.
>Inverters don't use iron cores, unless it's a big heavy inverter that
>uses a 60 Hz transformer. Is that what you're talking about?
>Otherwise, the transformer core is some kind of powdered iron or
>ceramic, not a terribly good heat conductor, and the copper windings
>are probably buried inside the core where a fan won't do any good.
Yes, I was thinking of the low freq ones for some reason. A fan will
make just the same difference with a powder cored TF. Look at the heat
paths I mentioned: just the same principle applies with a powder cored
TF. Same result.
I think Frithiof has just the right idea.
"Frithiof Andreas Jensen" wrote in message news:...
> "DaveC" wrote in message
> > of course. What are the critical specs I should focus on when looking for
> > upgrade?
> I would not bother replacing anything:
> First off: Measure the temperature rise of the heatsink for the FET's, the
> transformer (and any other component running hot) at rated load. This may
> require several hours for the temperature to stabilise!
> Next: Add a fan to blow air through the unit, heatsink & transformer should
> be in the airflow. Measure again. Increase the load (very) gradually until
> the temperature rise after several hours is the same as what you had without
> the fan.
> Measure the load -> this is what you can eek out of the unit with forced
> cooling. It will not be possible to improve this without major surgery -
> especially to the transformer.
> There may be overcurrent trips, fuses and other stuff preventing you from
> increasing the power. It is also dangerous - there is high voltage, heat
> sinks may not be insulated etc. You know what you are doing rite?
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