[Edward Morris]

Hello RAT'S. Is 55 Celsius too hot for an power transformer to run?

Thanks,
Edward Morris

[Phil Allison[_3_]]

"Edward Morris"

Hello RAT'S. Is 55 Celsius too hot for an power transformer to run?


** No.



....... Phil

[Ian Bell[_2_]]

Edward Morris wrote:
Hello RAT'S. Is 55 Celsius too hot for an power transformer to run?

Thanks,
Edward Morris


No.

Cheers

Ian

[[email protected]]

On Sep 23, 12:17*am, "Edward Morris" wrote:
Hello RAT'S. *Is 55 Celsius too hot for an power transformer to run?

Thanks,
Edward Morris

No, it is not. At the same time, is that when it is running Flat Out
or at Idle?

If at Idle, measure its temperature running Flat Out.

Peter Wieck
Melrose Park, PA

[Patrick Turner]

On Sep 23, 8:55*pm, " wrote:
On Sep 23, 12:17*am, "Edward Morris" wrote:

Hello RAT'S. *Is 55 Celsius too hot for an power transformer to run?

Thanks,
Edward Morris

No, it is not. At the same time, is that when it is running Flat Out
or at Idle?

If at Idle, measure its temperature running Flat Out.

Peter Wieck
Melrose Park, PA

55C is too hot IMHO.

It means that if you touch the tranny, you get pain.

I recently built a large PS using a 1.1kW tranny weighing 17Kg.

Initially, it didn't seem to want to get hot while drawing 700Watts.
So I potted in it in a steel box filled with casting resin.
Once potted and with the two class A monbloc amps connected, and when
the day temperature was 25C, the tranny temp wanted to rise to what
felt quite, warm, but I could keep a hand on the item for a minute
without pain so I estimated its temp at about 40C, so there is at
least a 15C rise. Internally, the winding T might be higher, but the
core material is low grade non oriented SiFe, and the iron losses are
somewhat high, and I estimated total losses to be mainly in the core,
but core plus copper losses would be about about 30Watts, or 5% of the
total output VA.
It took about 2 hours for the T to rise to 40C.

So testing transformer operating T must be done for a long time to see
what the real maximum operating T will be.

If you want less than 20C T rise for any item in an amp, you really
should have 40 square centimeters for each watt you have to get rid
of. In my case the steel box size surrounding the PT I have just used
in this PSU has about the right external area of over 1,200 sq.cm to
give a large enough surface area to prevent higher T than 15C above
ambient.

Had I had a tranny with GOSS instead of ther NOSS core the tranny
would barely get warm; maybe a 5C T rise.

Allowing trannies to run at run at 55Cm or say 30C above an ambient T
of 25C is *bean counter bull*****; ie, very poor quality design, and
it invites trouble, because the reliability of electronics reduces 10%
for each 10C rise in T.

To avoid the high T rise, you have to forgo the stupid idea to run the
tranny at say 1.3Tesla and you should run it at 0.9T max. This will
also have your tranny running more quietly, and with very low Fe
losses.

To achieve this you need 30% more turns than the bean counter
designers would use, and or 30% higher Afe, or a core that is GOSS.

The best PTs I have made myself have GOSS, have B = 0.85T, and have
the capacity to put up with continuous overloads of rated VA output
plus +50% without any smoke.

Patrick Turner.

[Phil Allison[_3_]]

"Patrick Turner"

55C is too hot IMHO.

It means that if you touch the tranny, you get pain.


** Laughable rubbish.

55C is the temp of a luke warm cup of coffee - only 17 degrees above body
temp.


Allowing trannies to run at run at 55Cm or say 30C above an ambient T
of 25C is *bean counter bull*****; ie, very poor quality design, and
it invites trouble, because the reliability of electronics reduces 10%
for each 10C rise in T.


** Total BUNKUM !!

A transformer is simply NOT an electronic component.

And power tubes typically run with plate temps of several hundred degrees C.


....... Phil

[Arny Krueger]

"Edward Morris" wrote in message

Hello RAT'S. Is 55 Celsius too hot for an power
transformer to run?

Depends on the operational environment.

In computers, we think that 120F is too much, and 140F is "On fire, remove
all power, and call the fire department". 110F is a nice, if a little bit
on the warm side. Body temperature ( ca. 40C) is really nice.

The idea that anything that is too hot to touch for long is too hot is a
good rule of thumb. That is somewhere between 110F and 120F.

Of course these temps indict just about every piece of consumer vacuum tube
equipment ever made.

I think that my old (tubed) Hawk radar equipment was based on temperatures
like 160F (cooling air flow) was the limit, and 140F was not uncommon. That
is about 60C and about 70C, respectively.

This 1960s military gear spent the big bucks trying to do everything right.
For example all the transformers were encapsulated in high temperature
epoxy, all the tubes were clipped to heat sinks, and all the wires were
insulated with Teflon. All caps were 80-90C rated.

We had some serious problems with reliability of certain chassis, and later
examination found that they were running at around at 180F.

In modern terms of modern temperature measurements and with some heavy
rounding, 40C is about optimum, 50C is too much, 60C is "on fire", and 45C
is a nice operating temperature, if a little warm. That all said, modern
insulation and semiconductors take high temperatures better than ever.

[[email protected]]

On Sep 23, 7:19*am, Patrick Turner wrote:

The best PTs I have made myself have GOSS, have B = 0.85T, and have
the capacity to put up with continuous overloads of rated VA output
plus +50% without any smoke.

Patrick, you build for the ages. That being written, 131F ain't half-
bad for a tube-use transformer running flat out under peak conditions
at highest expected ambient. Presumably it will run much cooler under
normal conditions.

Generally I run any piece of equipment that comes off the bench for at
least 4 hours before pronouncing it 'fit for polite society'. And in
my particular case, such society includes grand children from 7 weeks
to 6 years old, kittens, cats and dogs. A tranny running at 131F under
normal conditions would *not* be pronounced, as it were. Either it
would be caged, or kept away from common-area use.

But "too hot" is a very specific question - no, the typical
transformer will not fail at that temperature over the short term. And
if reasonably well built, it may last for a very long time. Not quite
the same thing as stating that such a condition is desirable.

Peter Wieck
Melrose Park, PA

[Edward Morris]

Thanks for the response guys. I bought a pair of Dyna MKII monoblocks with
the Triode board and the SDS power supply board. I only had one amp that
the power trannie was hotter than these monoblocks. It doesn't take long
(45 minutes) for the temperature to rise and I can't keep my hand on the
power trannie for any length of time. I have a pair of Klipsch La Scala's
so I doubt the temp at idle and driving is not at all that different. The
Triode board has 2 tubes instead of 1 tube with the stock board.

Though I'd question the massive amount of capacitance the SDS board has, the
5AR4 purrs like a kitten with no problem. In it's day, the power trannie
might of been underrated but with the boards, is probably quite a bit
underrated. I think the new drop in trannie from dynakitparts; the B+ is
rated at 200ma. Sometime in the future when the trannies bite the dust, if
they do, I'd like to have custom power trannies.

Patrick, you seem to know quite a bit about electronics. What should I ask
a transformer builder or ask them to do if I would have to have a
transformer custom made? I could measure the current of the B+, bias
circuit.the 6.3 and 5 volt circuits, but it is what it is so I don't see the
point unless one of the transformers went out, then the transformer builder
would have to know of the current I'm dealing with.

Thanks for the responses,
Edward Morris

"Arny Krueger" wrote in message
...
"Edward Morris" wrote in message

Hello RAT'S. Is 55 Celsius too hot for an power
transformer to run?

Depends on the operational environment.

In computers, we think that 120F is too much, and 140F is "On fire, remove
all power, and call the fire department". 110F is a nice, if a little bit
on the warm side. Body temperature ( ca. 40C) is really nice.

The idea that anything that is too hot to touch for long is too hot is a
good rule of thumb. That is somewhere between 110F and 120F.

Of course these temps indict just about every piece of consumer vacuum
tube equipment ever made.

I think that my old (tubed) Hawk radar equipment was based on temperatures
like 160F (cooling air flow) was the limit, and 140F was not uncommon.
That is about 60C and about 70C, respectively.

This 1960s military gear spent the big bucks trying to do everything
right. For example all the transformers were encapsulated in high
temperature epoxy, all the tubes were clipped to heat sinks, and all the
wires were insulated with Teflon. All caps were 80-90C rated.

We had some serious problems with reliability of certain chassis, and
later examination found that they were running at around at 180F.

In modern terms of modern temperature measurements and with some heavy
rounding, 40C is about optimum, 50C is too much, 60C is "on fire", and 45C
is a nice operating temperature, if a little warm. That all said, modern
insulation and semiconductors take high temperatures better than ever.

[fryzz]

Edward,

Dynaco tended to run their stuff on the hairy edge due to
considerations of economy. Their power transformers were most
definitely not overrated, in combination with the fact that the power
line voltages you see today are higher than than they were 40-50 years
ago, these transformers tend to run hotter than the hinges of Hades.
I like taking a 12 V@1A (or thereabouts) toroidial transformer and
hooking it up so the secondary is in series and out of phase with the
primary, which bucks the line voltage down by about ten percent,
enough to make a real difference without degrading performance.
Toroids are compact and flat, don't radiate much of a hum field, and
it's usually pretty easy to tuck them away somewhere underneath where
they're not visibe.

Frank

[radio guy]

On Sep 23, 12:17*am, "Edward Morris" wrote:
Hello RAT'S. *Is 55 Celsius too hot for an power transformer to run?

Thanks,
Edward Morris

My hot water is at 140 and that's not enough to really hurt you. For a
transformer a temp of 131 is no problem,don't worry about it.