"John G" wrote in message
. au...

It happens that Gareth Magennis formulated :

"John G" wrote in message
. au...

Gareth Magennis laid this down on his screen :

"Tom Miller" wrote in message ...


"Trevor Wilson" wrote in message
...
On 22/07/2014 4:18 AM, Fred McKenzie wrote:
I have a couple of 20 Amp linear DC power supplies with hot
transformers.

With no load, one gets up to 115 Degrees F after several hours. The
other gets up to 125 Degrees F. Measurements were made with an IR
thermometer looking at the top of the transformer. I disconnected the
secondary windings of one, but results were the same.

With their covers installed, neither power supply feels excessively
hot.
The one that got to 125, gets to 95 Degrees F on top of its cover with
about two Amps load.

One cause might be not enough iron in the core. I suppose there could
be some circulating currents in the core as well. Regardless, does
anyone know if they are hot enough to be a problem? Or should I just
not worry about it?

I checked several other power supplies, and none had transformers above
95 Degrees F.

Fred


**Most power transformers will operate at 100 degrees C quite safely,
though I prefer to see less than 75 C. I have no idea what 125 degrees F
is and I have no interest either, but I suspect it is less than 75 C.

[ASIDE] This is an international group. Almost none of the planet's
population (less than 5%) bothers with archane measurements, like
degrees F, anymore. Please learn the Metric system.

-- Trevor Wilson www.rapeaudio.com.au


Why, because you are too ****ing stupid or lazy to do a simple
conversion?




OK, convert the very accurate and reproducable measurement of 62.25cm, to
the Imperial system, and you get 24inches and 39/64ths.

That's a bit of a joke, surely, that should not be present in the 21st
century.


Gareth.

No it converts to 24.507874 inches if you us the same maths notation.




The point is that the Imperial system commonly uses discrete steps that
are only accurate to those steps.

The metric system does not suffer this limitation.


Gareth.

Neither does the imperial system if you use a rule marked in tenths and
Micrometers are marked in 1/1000s or some such and not fractions which
were near enough for woodworkers in the past.

PS I am no fan of Imperial either in measurement or in Government but
we have to live with rest of the world and be tolerant of whatever
comes by. :-Z





Some time ago I was employed to install the audio wiring in a new build
recording studio.
In one room, I was astounded to find the carpenter had pencilled in the
width of one wall using a measurement of feet, inches, and so many 8ths of
an inch.

So he was only working to an accuracy of 16th of an inch, which is 1.58mm.
To me, this is completely unacceptable in a professional environment, and
the basis of my posts in this thread.


Gareth.