Hot Transformer

[Fred McKenzie]

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

 

[RobertMacy]

On Mon, 21 Jul 2014 11:18:07 -0700, Fred McKenzie <fmmck@aol.com> 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

46C? and 50C no biggie

transformers are passive devices and made out of 'material'

easily take 65C, that's 150F

you may be running your AC mains at 125Vac instead of the 115Vac, which
will make them run just that bit hotter to where you noticed.

 

[Trevor Wilson]

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.rageaudio.com.au

 

[Tom Miller]

"Trevor Wilson" <trevor@SPAMBLOCKrageaudio.com.au> wrote in message
news:c35dk6F6oq6U1@mid.individual.net...

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 fucking stupid or lazy to do a simple conversion?

So why did you even take the time to make your stupid comments?

 

[Gareth Magennis]

"Tom Miller" wrote in message news:lqk5ap$vce$1@dont-email.me...


"Trevor Wilson" <trevor@SPAMBLOCKrageaudio.com.au> wrote in message
news:c35dk6F6oq6U1@mid.individual.net...

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 fucking 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.

 

[John G]

Gareth Magennis laid this down on his screen :

"Tom Miller" wrote in message news:lqk5ap$vce$1@dont-email.me...


"Trevor Wilson" <trevor@SPAMBLOCKrageaudio.com.au> wrote in message
news:c35dk6F6oq6U1@mid.individual.net...
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 fucking 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.

 

[Tom Miller]

"Gareth Magennis" <gareth.magennis@ntlworld.com> wrote in message
news:r2hzv.386849$cb.202294@fx15.am4...

"Tom Miller" wrote in message news:lqk5ap$vce$1@dont-email.me...


"Trevor Wilson" <trevor@SPAMBLOCKrageaudio.com.au> wrote in message
news:c35dk6F6oq6U1@mid.individual.net...
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 fucking 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.

Why not use 24.50 inches? Minding the significant figures.
It only bothers lazy people. But at least stay within one system.

Then there's pounds, shillings, pence, etc. Oh, at least you have the Euro.

 

[Tom Miller]

"RobertMacy" <robert.a.macy@gmail.com> wrote in message
newsp.xjc24hpo2cx0wh@ajm...

On Mon, 21 Jul 2014 11:18:07 -0700, Fred McKenzie <fmmck@aol.com> 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

46C? and 50C no biggie

transformers are passive devices and made out of 'material'

easily take 65C, that's 150F

you may be running your AC mains at 125Vac instead of the 115Vac, which
will make them run just that bit hotter to where you noticed.

One thing the OP failed to state is the voltage of his 20 amp power supply.
2000 volts at 20 amps is a much larger transformer then one might find in a
12 volt, 20 amp supply.

 

[John G]

Trevor Wilson was thinking very hard :

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.

Actually it is 51.66 deg C which is not to hard to figure and afterall
most of us down here have learnt over the years to cope with whatever
the underdeveloped world chooses to use. :-?

 

[Gareth Magennis]

"John G" wrote in message
news:uJ6dnRiyvok0P1DOnZ2dnUVZ_hSdnZ2d@westnet.com.au...

Gareth Magennis laid this down on his screen :

"Tom Miller" wrote in message news:lqk5ap$vce$1@dont-email.me...


"Trevor Wilson" <trevor@SPAMBLOCKrageaudio.com.au> wrote in message
news:c35dk6F6oq6U1@mid.individual.net...
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 fucking 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.

 

[John G]

It happens that Gareth Magennis formulated :

"John G" wrote in message
news:uJ6dnRiyvok0P1DOnZ2dnUVZ_hSdnZ2d@westnet.com.au...

Gareth Magennis laid this down on his screen :

"Tom Miller" wrote in message news:lqk5ap$vce$1@dont-email.me...


"Trevor Wilson" <trevor@SPAMBLOCKrageaudio.com.au> wrote in message
news:c35dk6F6oq6U1@mid.individual.net...
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 fucking 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

 

[William Sommerwerck]

**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.

It's such a big deal to convert, isn't it?

Start by subtracting 32. That's 93, which you can round off to 90. Then take
5/9 of that -- 50, which is close enough. You can do it in your head in a few
seconds.

There's no need to memorize the formula, if you remember that 0 and 32 degrees
are the same point, and 1 degree F is 9/5 degree C.

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.

First, it's spelled arcane (hidden, mysterious). Which isn't the word you
want -- you want archaic.

Metric is not capitalized.

 

[Tom Miller]

"John G" <john.g@greentest.com> wrote in message
news:loGdnSOACb8ERFDOnZ2dnUVZ_oydnZ2d@westnet.com.au...

It happens that Fred McKenzie formulated :
In article <lqk83s$g8m$1@dont-email.me>,
"Tom Miller" <tmiller11147@verizon.net> wrote:

One thing the OP failed to state is the voltage of his 20 amp power
supply. 2000 volts at 20 amps is a much larger transformer then one
might find in a 12 volt, 20 amp supply.

I am using these power supplies for Ham Radio equipment. Voltage is
supposed to be 13.8, but I think most people just say 12.

A temperature of 125ş F/52ş C is hotter than you want to hold your hand
on, but you probably will not scream from the pain. Temperature is a
significant factor in reliability calculations. I was concerned about
the long term degradation of components.

I think I just answered my own question. The hottest power supply is 30
years old and the other is 20. Both appear to meet their electrical
specifications.

Fred

Do they really meet their Specs?
Back then (30 years ago) the nominal in USA was more likely 110 volts
whereas today to follow Harmonisation rules it should be 120 which is a
like 9% increase. Of course there is a wide margin but you may be on the
high side. Just a thought.

Sounds like an Astron AS20 or similar. The transformers are made with cost
in mind and they do run hot even at no load.

As long as it doesn't smoke, I would not be too worried.

 

[Trevor Wilson]

On 22/07/2014 8:48 AM, Tom Miller wrote:

"Trevor Wilson" <trevor@SPAMBLOCKrageaudio.com.au> wrote in message
news:c35dk6F6oq6U1@mid.individual.net...
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 fucking stupid or lazy to do a simple conversion?

**There is no need to do the conversion. Hardly anyone bothers with
Imperial measurements anymore.

So why did you even take the time to make your stupid comments?

**I answered the question, correctly and succinctly. I also attempted to
educate the original poster in how to deal with an international
audience, by pointing out that a measurement system which is used in one
small corner of the planet may not be understood by the vast majority.

--
Trevor Wilson www.rageaudio.com.au

 

[Trevor Wilson]

On 22/07/2014 11:29 AM, William Sommerwerck wrote:

**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.

It's such a big deal to convert, isn't it?

**There is no need to convert. 95% of the planet's population uses
Metric measurements. The 5% left is irrelevant.

Start by subtracting 32. That's 93, which you can round off to 90. Then
take 5/9 of that -- 50, which is close enough. You can do it in your
head in a few seconds.

**I never need to perform such useless calculations. Almost every person
on this planet uses Metric measurements.

There's no need to memorize the formula, if you remember that 0 and 32
degrees are the same point, and 1 degree F is 9/5 degree C.

**There is no need to convert, nor memorise anything, anyway. Almost
every human on the planet uses Metric measurements in their daily lives.
ALL scientific measurements are done within the Metric system. The
Imperial system is just idiotic. Most of us humans naturally gravitate
towards a base 10 form of measurement. The Metric system is just plain
logical and extremely easy to live with.

[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.

First, it's spelled arcane (hidden, mysterious). Which isn't the word
you want -- you want archaic.

**Thanks for the spelling correction.

Metric is not capitalized.

**When I was taught the Metric system, it was capitalised. So,
capitalised it will remain (for me).

--
Trevor Wilson www.rageaudio.com.au

 

[Fred McKenzie]

In article <lqk83s$g8m$1@dont-email.me>,
"Tom Miller" <tmiller11147@verizon.net> wrote:

One thing the OP failed to state is the voltage of his 20 amp power supply.
2000 volts at 20 amps is a much larger transformer then one might find in a
12 volt, 20 amp supply.

I am using these power supplies for Ham Radio equipment. Voltage is
supposed to be 13.8, but I think most people just say 12.

A temperature of 125ş F/52ş C is hotter than you want to hold your hand
on, but you probably will not scream from the pain. Temperature is a
significant factor in reliability calculations. I was concerned about
the long term degradation of components.

I think I just answered my own question. The hottest power supply is 30
years old and the other is 20. Both appear to meet their electrical
specifications.

Fred

 

[John G]

It happens that Fred McKenzie formulated :

In article <lqk83s$g8m$1@dont-email.me>,
"Tom Miller" <tmiller11147@verizon.net> wrote:

One thing the OP failed to state is the voltage of his 20 amp power supply.
2000 volts at 20 amps is a much larger transformer then one might find in a
12 volt, 20 amp supply.

I am using these power supplies for Ham Radio equipment. Voltage is
supposed to be 13.8, but I think most people just say 12.

A temperature of 125ş F/52ş C is hotter than you want to hold your hand
on, but you probably will not scream from the pain. Temperature is a
significant factor in reliability calculations. I was concerned about
the long term degradation of components.

I think I just answered my own question. The hottest power supply is 30
years old and the other is 20. Both appear to meet their electrical
specifications.

Fred

Do they really meet their Specs?
Back then (30 years ago) the nominal in USA was more likely 110 volts
whereas today to follow Harmonisation rules it should be 120 which is
a like 9% increase. Of course there is a wide margin but you may be on
the high side. Just a thought.

 

[Gareth Magennis]

"John G" wrote in message
news:e5Gdnd3MwJwqNVDOnZ2dnUVZ_iydnZ2d@westnet.com.au...

It happens that Gareth Magennis formulated :

"John G" wrote in message
news:uJ6dnRiyvok0P1DOnZ2dnUVZ_hSdnZ2d@westnet.com.au...

Gareth Magennis laid this down on his screen :

"Tom Miller" wrote in message news:lqk5ap$vce$1@dont-email.me...


"Trevor Wilson" <trevor@SPAMBLOCKrageaudio.com.au> wrote in message
news:c35dk6F6oq6U1@mid.individual.net...
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 fucking 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.

 

[Tim R]

On Monday, July 21, 2014 5:04:09 PM UTC-4, Trevor Wilson wrote:

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.

While I agree in general with the sentiment, there is no actual advantage of C over F in doing calculations.

C and F are both European temperature systems based on 100 degrees. For C there are 100 degrees between the temperature at which water freezes and boils; for F there are 100 degrees between the usual hottest and coldest temperatures in Europe at the time.

 

[RobertMacy]

On Mon, 21 Jul 2014 19:30:16 -0700, Fred McKenzie <fmmck@aol.com> wrote:

...snip....
A temperature of 125ş F/52ş C is hotter than you want to hold your hand
on, but you probably will not scream from the pain. Temperature is a
significant factor in reliability calculations. I was concerned about
the long term degradation of components.

I think I just answered my own question. The hottest power supply is 30
years old and the other is 20. Both appear to meet their electrical
specifications.

Fred

Standard 'rule of thumb' the MTBF is halved for every 10C increase in
temperature.
(10C ==> 18F)