Kennan C. Herrick filed US patent 6,069,413, “Apparatus for generating an alternating magnetic field”, on 26 Oct 1998, and it was granted on 30 May 2000. It covers charged capacitors and transistors arrayed around a primary, switched so the field alternates. On 14 Nov 1999 he described his coil to the Tesla list. It took 115 V in, with 24 power MOSFETs of 85 A and 500 V in push-pull parallel driving the equivalent of one primary turn. At about 4 A and 50 sparks a second it gave 16 to 20 in from a 4 in toroid, and he planned 48 and then 72 transistors. By 18 May 2001 it gave about 3 ft in bursts of about 7 ms, from two equivalent untuned turns, 24 pairs of MOSFETs and about 200 A in the bursts. Dan McCauley's history of 2004 called it an OLTC-like push “back in 1995”. The patent and the posts say 1998 and 1999.
Schematics and photos
drawing: fig. 2 of the patent
Sources
- US 6,069,413, Apparatus for generating an alternating magnetic field (filed 26 Oct 1998)
- pupman.com: Kennan C. Herrick, 14 Nov 1999
- pupman.com: Kennan C. Herrick, 18 May 2001
This is the card from the driver tree, written from what the builder published. Send corrections through the forum.