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Old 20th October 2013, 02:03 AM   #541
AJT is offline AJT  Philippines
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Location: Palatiw, Pasig City
here is a newly built power traffo for a tube amp,
center leg is 1 3/4 and stacked to about 3 inches....
i rate this traffo at about 600volt-amperes...

i use a silicon sealant to seal off the edges of the windings to prevent moisture ingress,
the white sealant dries clear, it will take about a week for the entire traffo to be
fully dried and ready for service, prior to that i will do an open and short circuit test
to compare design data with actual conditions....

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Old 21st October 2013, 09:03 AM   #542
John8 is offline John8  United Kingdom
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I hope it is a neutral cure silicon sealant you have used. Some of them give off acetic acid during the cure phase and could attack the copper windings.
Saying this I used the wrong one to pot up an EHT tripler in a scope many moons ago but I applied it in thin layers waiting for each to go off before adding the next. It is still going strong after all these years.
Hopefully yours will be OK too and give you many years of service.
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Old 21st October 2013, 09:13 AM   #543
AJT is offline AJT  Philippines
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Quote:
Originally Posted by John8 View Post
I hope it is a neutral cure silicon sealant you have used. Some of them give off acetic acid during the cure phase and could attack the copper windings.
Saying this I used the wrong one to pot up an EHT tripler in a scope many moons ago but I applied it in thin layers waiting for each to go off before adding the next. It is still going strong after all these years.
Hopefully yours will be OK too and give you many years of service.

this is a non smelly type and shrinks as it cures, that is why it is okey to apply
in a bulging manner, it dries clear as well.....and most of all it is cheap to buy, very DIY friendly....
and you can use your fingers to form it, it is water soluble as well...
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Old 18th November 2013, 01:59 AM   #544
kbeist is offline kbeist  United States
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Default My rant/soap and input to this wonderful arena

What advantages or dissadvantages would placing a gap of x distance and y area have? I say y area because not all traffo gaps are total cross sectional core gaps. I know it would cause Bmax to increase thus inversly proportional to inductance. But what kind of core/copper losses would one encounter? To overcome the inverse proportions, by how much would one have to increase the # of windings? What generic core materials are/have been scavenged to plug-into some of these dynamic calculations? I have several transformers that I would like to know more about and instead of playing 21questions about each and every one that I have or would like to have (be it NOS, or purchased).

#RANT# Also what I have noticed is the fact that there are some DIYaudio members (Label:Troll) that instead of researching this vast topic of Electromagnetics, they tend to just pop-in a thread asking, "I have this square-ish heavy iron thing. Blah, Blah. I want to power my diy 500W amp. Do the math for me so I dont have to think about how I can get electrocuted rewinding it." A good bit of reading, power-searching, lengthy calculations that comprise an excellent/well built durable transformer will do more for your knowlege/experiance than for someone to do the brain-stuff while you go unashamedly "hands-on" with little to no knowlege. #END#

I am currently working on a semi-full featured spreadsheet that hopefully encompasess a good majority of transformer design calculations. I am trying to gather information that will lead to:
1) Assist in new constructed power transformer
2) Assist in estimating a reverse engineered on-hand transformer
3) Assist in gaining knowlege and respect for this facet of electrical/electronics
4) Assist in arming an individual with knowlege to determin if it is worth his/her time/effort/$$
5) I would like to include calculations without vast amount of explaination that includes Core material/frequency/Voltage/Current/Wire. (I am not sure if all this is possible given my current knowlege/understanding. However, I am willing to undertake this lengthy process.)

The toughest part of this so far is muddeling through the various "intrinsic"/"brute force"/"simplistic" calculations. I have already encountered 5 websites, 2 pdf's, 3 forum threads, and 1 blog that have either erronious/false/misleading information or they oversimplify the information needed. One fine example was one that I actually entered real information into a spreadsheet and it spit out a result of Turn/V=9e14, this was for a 480VA/120Vin-80Vout at 95mT!?! Another example was a short web page that basically described the losses within a transformer a function solely reliant on wire resistance vs. (current arbitrairly chosen according to awg). My definition of Powersearch = 4 -5 instances of IE with 8-15 tabs each. And away we go!!!
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Old 18th November 2013, 02:23 AM   #545
ChrisA is offline ChrisA  United States
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Quote:
Originally Posted by John8 View Post
I hope it is a neutral cure silicon sealant you have used. Some of them give off acetic acid during the cure phase and could attack the copper windings.
Saying this I used the wrong one to pot up an EHT tripler in a scope many moons ago but I applied it in thin layers waiting for each to go off before adding the next. It is still going strong after all these years.
Hopefully yours will be OK too and give you many years of service.
I notice he used the "cheap stuff" with the 5 year warranty. The better kind says 35 years on the tube. But this is better or worse for its intended purpose of outdoor weather sealing. The cheaper stuff might be better in for use with transformers.

This 5 year caulk is really not silicon seal. it is more like very think latex paint in the tube. There is silicon mixed in the acrylic but I suspect it is already cured and made into a powder and mixed into the acrylic.

I use this kind of caulk outdoors on projects that I want to cover with paint. I can put it on then smooth it with a wet towel as it is water soluble until it cures.
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Old 18th November 2013, 06:03 PM   #546
kbeist is offline kbeist  United States
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Another question that pohed-in my head. If a double "C" core were to be placed side-by-side without overlaping, and the Primary and secondary were to be wound on the newly created "center leg" producing a "quasi" EI. Would the calculations need to include an aditional "gapping factor"? Or would the 2 central legs be considdered 1 center tounge?The reason I ask is that I have noticed the lines of magnetic flux have been diagramatically shown to traverse through that area perpindicular to the coils and not cut through the cohersive force of the mag lines. What of eddy currents? Would they increase or decrease? I used to have several ballasting transformers that were "T&L" sections (deep in the dump by now).
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Old 18th November 2013, 08:00 PM   #547
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Best two things I've found for transformer design are:

Magnetics Designer Manual pdf [especially if you like maths, even the formulae to calculate leakage inductance and inter winding capacitances are contained therein, although I would think any such calculation could possibly be inaccurate, one of them is an integral of an integral of an integral !!]

and

High Reliability Magnetic Devices by McLyman [which contains the most practical winding techniques I've seen..in a book, good diagrams etc].

Sad to say I have mastered neither.

Specifically for audio is Pat Turner's website.
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Old 18th November 2013, 10:19 PM   #548
AJT is offline AJT  Philippines
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Quote:
Originally Posted by kbeist View Post
Another question that pohed-in my head. If a double "C" core were to be placed side-by-side without overlaping, and the Primary and secondary were to be wound on the newly created "center leg" producing a "quasi" EI. Would the calculations need to include an aditional "gapping factor"? Or would the 2 central legs be considdered 1 center tounge?The reason I ask is that I have noticed the lines of magnetic flux have been diagramatically shown to traverse through that area perpindicular to the coils and not cut through the cohersive force of the mag lines. What of eddy currents? Would they increase or decrease? I used to have several ballasting transformers that were "T&L" sections (deep in the dump by now).
yes, but you can get away with higher flux density, the mating surfaces need to very smooth...
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Old 21st November 2013, 08:24 PM   #549
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Originally Posted by AJT View Post
yes, but you can get away with higher flux density, the mating surfaces need to very smooth...
no, it is not generally possible to configure tape wound cores anyway other than the way they were designed.

also, my choke and transformer design spreadsheets have been updated
Index of /bulk/spreadsheets
.xls versions should work, but i don't trust them... just download open office...
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Old 21st November 2013, 09:04 PM   #550
tinitus is offline tinitus  Europe
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Hi, Tony, would it make sense to use laminated UI-core to make a balanced PP trafo ?
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