[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [TCML] secondary windings burning?

Dex and Jim,

Most hobbyist coils should use close winding to maximize inductance per unit length and average voltage/unit length. Very large coils typically do not use magnet wire, but instead use stranded wire with thicker polymer insulation - this "effectively" space winds the secondary. This is done for a variety of practical reasons such as increased winding flexibility, better resistance to handling or environmental damage and sometimes to reduce voltage stress per unit length.

Many different types of magnet wire can be used with varying degrees of success. However, for demanding coiling applications, heavy build 200C polyamide-imide (PAI) - Nylon and Kapton - is recommended. Heavy build 240C polyimide (PI or Kapton) magnet wire can also be used, but it tends to be significantly more expensive and offers no additional benefits to coilers. Polyamide-imide wire is designed for applications where high voltage transient voltage stresses and/or high temperatures are expected. Although other types of double-build magnet wire can also be used, your results may vary. The dual insulating layers combine to form a tough, low friction, abrasion-resistant coating that's also resistant to most oils and solvents.

Most important to coilers, heavy build (also called double build, heavy coat, armored...) PAI insulation is partial discharge and corona-resistant. This wire typically has a breakdown strength that exceeds 10 kV(!), so it can withstand exceptionally high turn-turn voltage transient and RF stresses without suffering breakdown. A close-wound single layer winding subsequently coated with a 2-part epoxy or polyester coating not only looks great, it will also perform well and be extremely resistant to corona or strike-related damage.

The wire should meet ANSI/NEMA MW35C. Some commonly used names or abbreviations for this kind of wire includes Heavy or Armored Thermaleze, Heavy or Armored Polythermaleze, APTZ, HPT, HAPT, HPAM, HTAI, HTAIH, GP200, MR200. Some of these designations are older terms, but may be of some use when purchasing off eBay.

Hope this helped...

We specialize in UNIQUE items! Coins shrunk by huge
magnetic fields, Lichtenberg Figures (our "Captured
Lightning") and out of print technical Books. Visit
Stoneridge Engineering at http://www.teslamania.com

Dex Dexter wrote:
Is it better to use space wound coils or close wound coils then?



Jim Mora wrote:
It may be useful to state the type of wire preferred. I used to think
Formvar was king - way off. However, The other day I landed on a reputable Mag wire site. It seems Polyamide rules. It has very high temp and highest dielectric strength by substantial margins.

Tesla mailing list