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#1
Posted to rec.audio.tubes
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Transfomer Temperature?
Hello RAT'S. Is 55 Celsius too hot for an power transformer to run?
Thanks, Edward Morris |
#2
Posted to rec.audio.tubes
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Transfomer Temperature?
"Edward Morris" Hello RAT'S. Is 55 Celsius too hot for an power transformer to run? ** No. ....... Phil |
#3
Posted to rec.audio.tubes
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Transfomer Temperature?
Edward Morris wrote:
Hello RAT'S. Is 55 Celsius too hot for an power transformer to run? Thanks, Edward Morris No. Cheers Ian |
#4
Posted to rec.audio.tubes
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Transfomer Temperature?
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 |
#5
Posted to rec.audio.tubes
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Transfomer Temperature?
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. |
#6
Posted to rec.audio.tubes
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Transfomer Temperature?
"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 |
#7
Posted to rec.audio.tubes
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Transfomer Temperature?
"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. |
#8
Posted to rec.audio.tubes
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Transfomer Temperature?
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 |
#9
Posted to rec.audio.tubes
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Transfomer Temperature?
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. |
#10
Posted to rec.audio.tubes
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Transfomer Temperature?
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 |
#11
Posted to rec.audio.tubes
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Transfomer Temperature?
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. |
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