Nov 5, 2012
Alberta Chu: How is it safe to be inside the Electrum’s sphere while measuring streamers?
Greg Leyh: Electrum was also the first coil designed to operate at power levels higher than 100,000 watts. This required developing a unique 4-armature rotary gap design, 3-phase-to-DC power conversion, and a finite-element high voltage electrode design large enough for a person to climb inside.
After we got the Electrum working, we had to operate it a maximum capacity for a required number of hours in order to test it. These turned into big events in San Francisco. We even got the chance to stage some performance art of our own. Oddly enough, the space inside Electrum’s high voltage electrode is one of the safest places to be while the coil is operating. The person inside the electrode is protected by Faraday’s Law, which states that the electric field inside a conductor is zero. Ironically, the audience standing around the coil is exposed to much higher electric fields as they marvel at the brave soul inside the electrode. A couple of months after this photo was taken, we shipped the Electrum off to New Zealand.
AC: We’re all dying to know - how does one build the world’s largest tesla coil? Tell us about the unique ‘firsts’ for the Electrum sculpture.
Greg Leyh: The Electrum sculpture lives outdoors and needs to withstand exposure to a harsh seaside climate for decades. This is definitely a first for Tesla Coil design. To guard against the harsh environment the entire coil form was literally built ‘inside-out’ -- The secondary coil is molded to the inside wall of the cylindrical fiberglass tower, and the primary drive coil resides *inside* the secondary coil. Although there was no precedent for this approach, calcs and simulations supported the idea, and ultimately the test of time proved it out.
The Electrum consumes the power of 50 homes when it’s being operated.
AC: You visited the Farm to do a tune-up on the Electrum a couple of years ago - how did you find things there?
GL: In 2009, about 10 years after the initial installation, I was asked to visit the Farm and diagnose an apparent internal arcing issue with Electrum. Fearing the worst, I brought a full complement of diagnostic gear, and scheduled 10 days to work on the problem. As it turned out, the salty environment had managed to corrode an open hole through a 3/8” steel plate at the top of the tower, allowing saltwater, cobwebs and bird guano to freely enter and completely coat the high voltage windings inside the tower. Fortunately there was no permanent damage, and I only had to spend a couple of days hanging from a rope inside the tower, cleaning the winding surfaces. Once cleaned and the steel plate replaced, the coil ran just like I remembered. Aside from Electrum, the Farm itself changed dramatically between 1998 and 2009. So many new and incredible sculptures. I walked around the extents of the Farm for days. It’s a fantastic, very meditative place.
TO BE CONTINUED
San Francisco High-Voltage Engineer Greg Leyh, the builder of the world’s biggest tesla coil, will be appearing in-person at the Boston Museum of Science on November 7th, 2012 @ 6:45 pm to present the world premiere of filmmaker Alberta Chu’s documentary “Lightning Dreams: The Electrum at Gibbs Farm.” Greg will give a presentation about the proposed Lightning Foundry project, followed by a reception in the Theater of Electricity. Buy your tickets in advance: http://www.mos.org/events_activities/events&d=5620