Binding Agent to be Used as Insulation in Ultra High Frequency Applications

Insufficient information.

You need to look at the electrical properties of the SPECIFIC epoxy compound you are using. Simply stating Araldite is not good enough. There are many grades of the product. Look at the data sheet for the one you are using.

You need a materials specialist to determine the correct material for your specific application. Dielectric constant and loss are two properties to consider.

Teflon is a fine choice, and consider glass micro-spheres as a filler in your epoxy, whatever it is. It will lower your losses.

Finally, as is the case any times here, your answer probably will not come from an anonymous forum, but rather from someone whom you have direct conversations and an exchange of detailed knowledge.

Talk to an engineer at the supplier's factory. That's their job.

300 to 400 Khz is Low Frequency, unless you're speaking of sound. 300 to 400 Mhz is UHF, but at the low end.

We're all over the spectrum here, "high frequency applications along with teflon sheet as seperator in ultra high freq. applications".

What's a few megahertz among friends?

While the coil geometry is nice to know, the volume of space it occupies is not relevant to performance. To make a real comparison the number of turns, combined with the geometry of these coils, the geometry of the magnetic field path and the magnetic permitivity of this path will determine the inductance.

My WAG without knowing these details is that the some core material is saturating. This will dramatically drop the impedance at full power and thus raise the current drawn.

Dear Sir,

Thank you for the reply. The Inductor is consisting of 3 turns of 5mm copper tube ,out of which the outermost turn is soldered to a bottom solid copper ring through which only coolant flows and supply is given to the 3 turn coil along with DM water for cooling.The interturn gap is isolated with Mica tape,and the circular coil is cut at ends of which leads are provided, In the gap where the coil is cut , we have used teflon sheet of 1 mm along with araldite and also all three turns are cast in araldite epoxy. Pl. clarify whether araldite clear -- a fast curing epoxy adhesive is suitable or not for 5 Kw and 300 Khz power.

Sorry but I do not know the chemical composition of Araldite® epoxy. You should contact the manufacturer for this information. I would be surprised to find this epoxy has any dielectric or magnetic permitivity characteristics that could change the reactive electrical impedance of this coil but I've been surprised before.

A three turn coil will not have a very high inductance without some core material inside the coil. This means that the cable run from power source to coil can be just as large of an inductance as this coil.

Good Luck finding out what is different.

At that frequency, it doesn't matter.

Please provide a labelled sketch or photo(s) with annotations.

You're trying to reverse engineer an induction heater, right?

300kHZ is not a power measurement.

What is the P-P or RMS voltage of your supply?

You should use Mica with least possible thickness of binding material such as epoxy.

epoxy is a good electrical insulator but here please note that

1. Mica and Binder form insulations in series.

2. The applied voltage and dielectric losses will divide between two capacitors thus formed in series in proportion to Dielectric Constant of two materials.

3. Of all known insulations, Mica has the lowest Dielectric Constant. I do not know of Teflon or the commercial epoxy you are using.

Value for Teflon shall be available on net.

For value of Dielectric constant of epoxy, better use known electrical varnish ( two part, say poly amide based etc.) whose value shall be available in data sheet of manufacturer. Since your coil is water cooled hence its operating temperature will remain below 100 Deg C - you can chose safely any class B varnish binder

If you plan to replace mica with Teflon then thickness of Teflon and binder shall be inversely proportional to the dielectric constant of two

- but would still suggest to use mica and known binder

- apply minimum thickness of binder to hold mica folium pieces together (Hint - heat up the binder slightly so that its viscosity is reduced and extra thickness can be squeezed out easily leaving desired thickness to bind the mica)