Jos,
No this isn't transparent. It's a type of paper they make and use clay somehow
with the fibers. It is used for transformer layer insulation, and in the slots
of motor stators. It comes in different thicknesses from around 5 mil up to
thick card stock like about 60 mil. Its voltage rating is probably around 100
volts+ per mil, or is what we use as a rule of thumb. It could actually be more
than that though. 20 mil is used between the full coils, and the 5 mil between
each layer of a coil. 20 mil will also work as a bobbin but I like it a little
thicker, around 30 mils at least. Peter Dahl did have a photo of a transformer
using it on his website. It was a large one they had not dipped yet. You can
see though from the photo that he still uses the same stuff everyone else does.
He started using a black dye in his varnish. Then you had to add it to the
varnish, but now you can buy it with it in it. The black color supposed to help
with heat transfer. Now how good it is for that, I couldn't say as I've never
used it. I'm pretty sure I seen that paper for sell at Oceanstate Electronics.
Below is a link to their website.
http://www.oselectronics.com/
Best,
Will
*********** REPLY SEPARATOR ***********
On 4/14/06 at 10:27 PM hermans wrote:
>Will,
>
>The bleu shining stuff you'r talking about, could that be what we called '
>TRIAFOLL '.Shiny on one side, matt on yhr opther . We used that bleu nearly
>transparant isolating layers in transformers. Its kinda mica, and it holds
>very high voltages AC and DC as well. I still hold a roll of 26 x 0.2 mmm
>might be more then 100M.
>
>Jos on4kj
>
>
>-----Message d'origine-----
>De : amps-bounces@contesting.com [mailto:amps-bounces@contesting.com] De la
>part de Will Matney
>Envoyé : vendredi 14 avril 2006 21:35
>À : amps@contesting.com
>Objet : Re: [Amps] dielectrics for PAs TSPA
>
>
>John,
>
>Thanks, that was very educational and a very good read. I have an old book
>here that might be a good read for some on varnished cloths. It's titled
>"Varnished Cloths For Electrical Insulation", by H. W. Chatfield Ph.D., and
>J. H. Wredden. The book is copyrighted 1947 by the Chemical Publishing Co.
>There's no ISBN number. It gets into glass, cotten, etc including Micarda.
>This is still used in the transformer industry in sheets and tape. It
>explains a lot about how they should be used, etc. I know I learned a lot
>from it. I'll try to locate a copy of the book you mentioned as it would be
>a good reference.
>
>Best,
>
>Will
>
>*********** REPLY SEPARATOR ***********
>
>On 4/14/06 at 2:01 PM John T. M. Lyles wrote:
>
>>Will asked, and the floodgate opens:
>>
>>>What did you find good for use in the plastics
>>>as I'm interested about that myself?
>>>
>>
>>Thin Teflon sheet stock would make excellent
>>chimney, easy to make. Also, others have stated
>>that RTV silicone sheet does. Actually PET may be
>>a decent insulator in thin sheets. You can get
>>Mylar or even pop bottles and try them. Problem
>>there is the low melting point, but the anode of
>>a tube should not be 200 deg C!
>>
>>Here is a posting I made Jan 24, 2000 from the
>>archives of AMPS@contesting.com about dielectrics
>>for coil forms. G10 is probably OK for chimneys
>>when the voltage is reasonable, although my
>>experiences with it using 15,000 volts and higher
>>at 27 MHz were disasterous.
>>
>>>Subject: [AMPS] dielectric losses
>>>From: jtml@lanl.gov (John T. M. Lyles)
>>>Date: Mon, 24 Jan 2000 09:26:51 -0700
>>>
>>>I've been meaning to get back to the dielectric materials topic with
>>>some suggested alternate materials:
>>>
>>>At 11:50 PM -0500 1/15/00, owner-amps-digest@contesting.com (RF
>>>Amplifier Discussion Dige wrote:
>>>>I have been advised NOT to use Teflon, Delryn, and a few other
>>>>insulating materials for an RF choke. Instead only use ceramic. It
>>>>was then stated the "D" factor was the reason.
>>>>
>>>>OK, but why as I could not find info on this subject in the ARRL
>>>>Handbook. Any help to point me in the direction of knowledge on this
>>>>subject would be appreciated. May as well learn something while
>>>>building my amp. And I want to do it RIGHT.
>>>
>>>The following reply is correct, thanks Dave for inserting facts into
>>>that discussion.
>>>
>>>>Teflon is a (fluorocarbon resin) or (flourine plastic) and has the
>>>>same structure as polyethylene, in which the hydrogen is replaced by
>>(flourine).
>>>>OR a part may be replaced by (chlorine), in which case it is called
>>>>a (fluorohalocarbon resin).
>>>>
>>>>Polymerized (tetrafluoro ethylene), aka PTFE, which carries the E.I.
>>>>du
>>Pont
>>>>trade name of Teflon, formula (CF2*CF2)n is probably the most
>>>>common solid form used for insulating materials, bearings, gaskets,
>>>>insulating tapes, wire insulation, etc. This is a white waxy solid
>>>>with specific gravity of up to 2.3, typical tensil strengths of up to
>>>>3500 psi,
>>elongation
>>>>of 250-350%, dielectric strength of 1000 v/mil and melting point of
>>594*F.
>>>>
>>>>Another commonly encountered material in electronic use and sometimes
>>>>referred to generally as "Teflon", is Teflon FEP, which is a
>>>>fluorinated (ethylene-propylene). In thin films (typically down to
>>>>0.0005"), it is
>>most
>>>>frequently found as insulation in capacitors. Typical tensil
>>>>strength is 3000 psi, elongation 250%, and dielectric strength 3200
>>>>V/mil.
>>>>
>>>>Neither PTFE or Teflon FEP emit phosgene upon decompositon at
>>>>elevated temps.
>>>>
>>>>However, fluorothene plastic (which may be what Rich's info was
>>referenced
>>>>to) has the formula (CF2*CFCL)n and differ from (Teflon) in having
>>>>one chlorine atom on every unit of the polymer chain, replacing the
>>>>4th fluorine atom. This is a (transparent) material with a specific
>>>>gravity
>>of
>>>>~2.1, has tensil strengths of up to 9400 psi, but has a lower
>>withstanding
>>>>temp (as related to Teflon) of around 300*F. This material is
>>>>sometimes called "Teflon" due to its similarity in chemical and
>>>>polymer-structure make-up, and will emit phosgene upon decomposition
>>>>at elevated temps.
>>>>
>>>>73, Dave, K1FK
>>>
>>>
>>>I worked for E. I. DuPont in RF reseach in the late 1980s. We made a
>>>LOT of dielectric measurements up to 3 GHz. We used Teflon* as a base
>>>material (a substrate or boat) in a lot of heating experiments in high
>>>power RF. It is one of the best materials to use. Even when there is a
>>>direct arc, unless it burns deep into the material, it can be reused
>>>without repeat arcing. Teflon* is also rather inert, so it does not
>>>readily combine with other chemicals in experiments. Surface
>>>arc-resistance of pure Teflon* PTFE (* DuPont trademark) is excellent,
>>>and carbonized arc paths do not easily form on the surface. As others
>>>have already mentioned, the dielectric losses are among the best for
>>>polymeric materials (or even natural materials besides gases like air
>>>and vacuum). It is often used in radomes and in microwave windows. But
>>>it cold flows very easily, so if clamped or mechanically held, it will
>>>eventually deform. So it is rarely used where mechancal strength is
>>>needed. Coil forms should be no problem, for smaller coils wound with
>>>magnet wire, however.
>>>
>>>There is a sickness called the Teflon* flu. Machinists can get it when
>>>working the material at higher temperatures near the smoking point.
>>>This is to be avoided. It was not phosgene gas, but a fluorine
>>>byproduct I think. I don't know how harmful it is, but sounds like
>>>Rich's friend succumbed to an extreme case, or something else.
>>>
>>>The following Teflon* safety information came from E. I. du Pont de
>>>Nemours and Company website: "Before using Teflon®, read the Material
>>>Safety Data Sheet and the detailed information in the "Guide to the
>>>Safe Handling of Fluoropolymer Resins, Latest Edition," published by
>>>the Fluoropolymers Division of The Society of the Plastics
>>>Industry-available from DuPont.
>>> Open and use containers only in well-ventilated
>>>areas using local exhaust ventilation (LEV). Vapors and fumes
>>>liberated during hot processing, or from smoking tobacco or
>>>cigarettes contaminated with Teflon® or Tefzel® fluoropolymer resins,
>>>may cause flu-like symptoms (chills, fever, sore throat) that may not
>>>occur until several hours after exposure and that typically pass
>>>within about 36 to 48 hours. Vapors and fumes liberated during hot
>>>processing should be exhausted completely from the work area;
>>>contamination of tobacco with polymers should be avoided. Mixtures
>>>with some finely divided metals, such as magnesium or aluminum, can
>>>be flammable or explosive under some conditions. "
>>>
>>>
>>>A lot of flexible conveyor belts for RF heating systems in industry,
>>>use glass-reinforced Teflon* FEP polymers with silicone rubber. They
>>>don't get very hot in the intense RF fields used to heat polymers.
>>>
>>>To circumvent the weak mechanical properties, microwave industry uses
>>>crosslinked polystyrene, such as Rexolite, Polymer Q200.5, and maybe a
>>>few other tradenames. This stuff is the hard brittle plastic that is
>>>translucent, although it can be polished to be like glass. We use it
>>>to carry 3 Megawatts of RF, as the spider in our 14 inch coaxial lines
>>>in my present work. We buy it in 4 foot sheets, and cut and turn the
>>>discs. We have a special polishing wheel that looks like a phonograph.
>>>Rexolite does leave a carbon track when arced, and it can really melt
>>>into a goo if ignited. But the dielectric properties are only slightly
>>>inferior to Teflon*. K is 2.55 instead of 2.05-2.1. Loss tangent is
>>>still 0.000x range. Its good mechanically. By the way, 3 Megawatts is
>>>about 12 kV RMS, assuming perfect match in the coax line. It is worse
>>>than this, because of the high VSWR during off tune (Q of our load is
>>>60,000).
>>>
>>>Another material used a lot is ultra high molecular weight
>>>polyethylene or polypropylene -also called UHMWPE. This stuff is soft
>>>like Teflon*, a lot cheaper, and has good low loss, if you are careful
>>>in what you spec and buy. However, it is very easy to get the wrong
>>>material, so a dielectric test is really needed before designing with
>>>a piece. This stuff is used for waveguide windows sometimes.
>>>
>>>Amateur applications of lower RF voltage and frequency can get by with
>>>materials such as PVC, G10, maybe even Delrin (very questionable to me
>>>though). In high voltage RF service, in the VHF region, none of these
>>>can be used, due to excessive losses. Believe me, I have tried them
>>>all. I have a standard test i perform, in a 90 MHz dielectric heater,
>>>putting about 15 kV peak RF across a small block. In a few minutes,
>>>most of those materials will either burst in flames, or will begin to
>>>smoke and stink, as they are internally cooked.
>>>
>>>If you want to use fiberglass materials, G7 has lower loss than G10 or
>>>G11, due to the use of silicone instead of the more lossy epoxy resins
>>>in the other. It is harder to machine and cannot be turned for coil
>>>forms, we tried it 2 years ago and it just delaminated and fell apart.
>>>For the RF choke in the 100 kW 2.8 MHz amplifier, where the coil is
>>>exposed to the E field alternating at the plate of the tube, I chose
>>>polysulfone rod. It is easier to machine than Rexolite (crosslinked
>>>Polystyrene), and has fairly good dielectric properties. It is sold
>>>under one tradename UDEL* or Thermalux*. We are now using this same
>>>material for HV insulator posts for a 90 kV klystron power supply (not
>>>AC dielectric problem, only DC standoff).
>>>
>>>Another interesting new material is polyetherimide. This is
>>>trademarked as ULTEM* by GE and Westlake Polymers and Hydex* by
>>>Polypenco/DSM Polymers, I think. It can be had in glass reinforced
>>>sheets, and has good RF properties. It is expensive but very strong
>>>for mechanic support, such has holding an 80 pound tetrode so that it
>>>does not crash into the finger stock at the bottom of the filament
>>>connector in the socket.
>>>
>>>There are numerous other materials that are good, mostly more
>>>expensive, like polyimides Torlon* and Vespel* with incredible
>>>strength due to glass loading, etc. These are really beyond the range
>>>of most of us. They should be considered in cases where the ionizing
>>>radiation (gamma, Xrays) is high, and temperatures are high.
>>>
>>>The BEST reference book on dielectrics is still one of A. Von Hipple's
>>>books "Dielectric Properties and Materials", MIT. Long out of print,
>>>but I heard that they got reprinted not too long ago. Of course, these
>>>texts don't have all the modern miracle polymers that I refer to
>>>above.....
>>>
>>>If it works for you, then use it. But be aware that it may smoke now,
>>>or later, when moisture is absorbed in your material. Pick something
>>>that is not very hydroscopic if you live in a more humid climate than
>>>I do in New Mexico.
>>>
>>>73
>>>John
>>>K5PRO
>>>
>>
>>
>>
>>Here is another posting is from the March 24, 2004 archive:
>>>G10 will melt down into an awful stinkin' and
>>>burnin' mess when heated in high Rf fields. I
>>>rarely use it anymore, except for PW
>>>applications. It is certainly a big step above
>>>Delrin acetals or nylons. Have settled on
>>>several wonder materials like:
>>>Rexolite (crosslinked polystyrene) rod and sheet
>>>Polyetherimide (ULTEM* 2300) with 30% glass, also known as Tempalux*
>>>Polysulfone (UDEL*), also known as Thermalux*
>>>G7 (silicone resin reinforced glass)
>>>
>>>All more expensive, but if you want the highest
>>>Q and no heating, they are worth it. These are
>>>all high temperature engineered plastics. If you
>>>are concentrating E field flux in the
>>>dielectric, even with a kW, G10 will heat up.
>>>Good old UHMW (ulta high molecular weight)
>>>polypropylene and polyethyline made good
>>>insulators but have low glass transisition
>>>temperatures and will soften and dimensionally
>>>change with heat.
>>>
>>>Your local plastics supplier has them.
>>>Pricewise, the first two are about $1000 for a
>>>square foot of 1 inch thick material! The rod
>>>stock is much cheaper, and for smaller coils it
>>>is more so. The G7 is more difficult to machine
>>>or turn on a lathe than G10 due to the
>>>lamination layers. But it is excellent material
>>>structurally as well as RF'ly.
>>
>>_______________________________________________
>>Amps mailing list
>>Amps@contesting.com http://lists.contesting.com/mailman/listinfo/amps
>
>
>
>_______________________________________________
>Amps mailing list
>Amps@contesting.com
>http://lists.contesting.com/mailman/listinfo/amps
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|