[Amps] Ebay and engineering books

[Will Matney]

Jeff,

Yea, I have the one by Ruben Lee. I can see why Dahl would recommend it as it has some in there about Hipersil C-Cores. If I recall, it shows some used by GE called spiral-core or something similar. It does show the same basic transformer formulas, and what I couldn't figure by it having C-Cores is it didnt have the WA product formulas if I recall. The WA product is the window area x the core area, and is used to determine the power capability of any odd shaped core. Since C-cores are made in bookoos of sizes with odd window dimensions compared to the core area, that's about the way your supposed to do it. Matter of fact, Magnetic Metals show the WA product for each C-Core in their catalog. The other transformer formulas will work, but if the core has a really long window compared to the core area, the power rating can be off due to the magnetic path length. Most formulas that are used for EI construction take into consideration the scrapless EI design where all the windows come out to a certain dimension compared to the core area each time. In other words the window width is generally 1/2 the core tang width, and the window height is 1/2 the transformers whole width. For 60Hz, the area can be calculated from 0.1725 x sqr rt of the power in watts or volt amperes (watts if the load is resistive). Using that with a C-core though, with long windows, will be off some I would think.

The ones by McLyman show a new way of calculating cores also called the K factor, I think it is, which I've not tried yet, just read about. I think though it's something similar to the WA product except that he has some pre-determined factors to use for temperature rise, etc.. One thing I noticed, and didn't agree with, was a formula in there to determine the power required by the secondary which pretty much would say everything had to be multiplied by two. This has to do with efficiency and he put a +1 on the end of the division which makes it come out that way. A bridge rectifier with capacitor input uses about 1.6 to 1.8 for the multiplier in most formulas I've seen, and according to how big the filter cap is. A full wave center tap uses less, and if I recall supposed to be X1. You can find that in the core design book by him, and see what I mean.

I have a book here on staurable reactor design that shows some problems with any tape wound core like a C-core or a toroid. It shows they have more losses than an EI does of the same material. I'll look up the name of the book and share it here. I dug into this and sure enough, it was correct. Check Magnetic Metals website for the C-Core loss curves, and then Tempel Steel for the EI materials loss curves. Tempel bought the EI line from Magnetic Metals so it's their work. Microsil, Hipersil, and M-6 is the same alloy, and what to look up for any watts per pound loss curves.

Best,

Will



*********** REPLY SEPARATOR  ***********

On 2/16/06 at 9:16 PM Xmitters at aol.com wrote:

>In a message dated 2/16/06 6:10:03 PM Central Standard Time, 
>amps-request at contesting.com writes:
>
><< Actually, I have gotten some real deals off ebay, you just have to keep 
>looking for them. My whole electrical/electronic, and mechanical
>engineering 
>library came from there with a few through Abe Books, and Alibris. I
>bought 25 
>books at once off one seller for an average of $1.25 each, and were all
>very 
>good electronic books. I just bought a transformer book by William McLyman
>that 
>regularly sells for $115+ on there for $10 off a guy. There's another one
>left, 
>the link below. I bought the one titled "Transformer and Inductor Design 
>Handbook". The one that's left which goes with it, and by the same author
>is 
>titled "Magnetic Core Selection for Transformers and Inductors" which I
>already 
>had. That's a really good deal off the prices everywhere else including
>Abe 
>Books. Anyhow, I probably have about 200 books on electronics alone, not
>counting 
>mechanical engineering, and most were from ebay over the years. If I want
>one, 
>I never buy the first one I see and may wait months until 
>  I see a good deal and buy it. I have done like you mentioned and posted
>a 
>book I need and a book seller will contact me. It's all in playing the
>game for 
>a good deal. I'll check those others out you mentioned, they may have 
>something I want.
>  >>
>
>Will:
>
>Those two books are published by Dekker and they are very good books. I
>got 
>mine from the publisher and paid through the nose. 
>
>Another good transformer book, maybe you covered this one already, is a
>work 
>written by Ruben Lee, Electronic Transformers and Circuits. This one was 
>recommended to me by the friendly folks at Peter Dahl company. It is a
>great book 
>if you like that transformer math. If you like high power stuff, there is
>the 
>J. & P. Transformer Book published by Butterworths. It covers those power 
>substation monsters but the electrical/magnetic math is the same with
>interesting 
>stuff about cooling and failure modes as an extra added bonus. Makes for
>very 
>enjoyable reading on the train if you are not into War and Peace.
>
>No doubt, Ebay is a wonderful source for books and many other things. I
>buy 
>from Ebay too and have gotten some good deals there. My point was that you
>do 
>not have to rely on Ebay for good used books at fair prices. 
>
>I have a book I bought and have not opened it since I bought it. It's
>called 
>The Universal Vade Mecum and it is a tube data book complete with curves.
>The 
>end boards are slightly twisted because of the goofy way it was sitting on
>my 
>library shelf, but in otherwise new condition. I would like to see someone 
>adopt this book and give it a new home. I raided Fort Knox to pay for this
>book 
>too. I also have a three volume set of Tung Sol data sheet books, about
>four 
>inches thick each, I would love to dump. Anyone here interested in this
>kind of 
>stuff, please write. There are some other books I want and I need some 
>spending $$$.
>
>Anybody out there have a manual for the AN/FRT-72 100 kW transmitter
>laying 
>around just collecting dust? I love that high power stuff and I sure would
>like 
>a copy of this manual.
>
>Jeff Glass
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