900VA SGTC

The secondary structure of a tesla coil should be made of a substance of low loss. Materials such as polycarbonate (Lexan) or acrylic (Plexiglass) are appropriate. The coil form should be as thin as feasible, but must have enough strength to support the winding procedure and to sustain the Toroid terminal. A Tesla coil secondary has its own particular electrical makeup determined in part by the length of secondary. Like a tuning fork, it wants to vibrate at a particular frequency. The secondary is inductively energized by the primary coil.

The first secondary for this 1800 AC machine was a five inch form wound with AWG24 magnet wire on a 5 inch plexy glass form with a sealed top and bottom. The five inch secondary was 30 inches long and had about 29.5 inches of windings. There was 48 windings per inch. 1416 windings total, 1852 feet of wire was used to wrap this coil. There is 18 coats of varnish on this 5 inch coil . See first three pictures on left for 5 inch coil form.

After rev 3.8 I decided to make a new secondary, a six inch wound with AWG22 magnet wire on a 6 inch plexy glass form with a sealed top and bottom using plexy glass again. This larger form reduced running frequency which reduced power loss due to heat and skin effect. The six inch secondary was 30 inches long and had about 29.5 inches of windings. There was 38 windings per inch, 1121 windings total, 1,760 feet of wire was used to wrap this coil. The running frequency of this coil is 139.8 Khz. There are 40 coats of varnish on the six inch coil. The bottom picture is comparing the 5 inch to the 6 inch secondary.