For a KW level HV transformer, is there much difference between the temp that
you can touch and measure, say at the outside laminations, and perhaps the more
important temperatures in the core center, and the copper wire, bobbins,
windings, and paper/plastic insulation materials that we cannot see, inside?
And, a related question, from a cold room temperature start, if you could
measure the surface temperature of the laminations of a, say, Heathkit SB 220
amp that was being used with a lot of transmit time, on CW at 1KW out, How
long would it be before the outside lamination temperature could give a
representative temperature of the more critical inside core temperatures?
Could there be, say, 50 degree F temperature difference between inside and
outside when the Amp is producing 1KW RF output? If you can cool the outside
of the transformer with continuous airflow from a muffin fan, or better, would
that reduce significantly the inside core temperature?
Best Regards,
73, de Pat Barthelow AA6EG
> From: dezrat1242@yahoo.com
> To: amps@contesting.com
> Date: Fri, 11 Jun 2010 09:57:59 -0700
> Subject: Re: [Amps] Transformer Calcs
>
> ORIGINAL MESSAGE:
>
> On Thu, 10 Jun 2010 19:24:58 +0100, "Dr. David Kirkby"
> <david.kirkby@onetel.net> wrote:
>
> >Personally I would have thought just because a transformer is not too hot to
> >touch, it would not be safe to assume it is ok. I've run many transformers
> >up to
> >their maximum ratings and they are nowhere near being too hot to touch.
> >
> >The perception of too hot will also change with person. I recall once
> >finding a
> >radiator too hot to touch, but someone else could hold their hand on it
> >continuously.
>
> REPLY:
>
> I stand by what I said. Heat is the enemy of transformers because it
> deteriorates the insulation. I agree the concept of "too hot to touch"
> varies from person to person, but not that much. Transformer ratings
> furnished by a manufacturer are not an exact science either. Some will
> be conservative and some not.
>
> Run your transformer cool and it will last a long time. Run it hot and
> get ready to buy another one.
>
> 73, Bill W6WRT
> _______________________________________________
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> Amps@contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
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