Solid State Tesla Coil #1
Introduction
Here are some pictures of my latest science project - a Solid State Tesla Coil. I was sitting in a Microwave Traveling Wave Tube class one day
listening to a brief lecture on solid state cathode pulsing of the traveling wave tube and immediately began thinking of tesla coil. After researching
solid state tesla coils on the web, I've actually decided to build one myself. Instead of trying to re-invent the wheel, I basically borrowed portions
of solid state tesla coil designs on the web and started from there. In the above picture, the mains breaker / switch is to the left, the tesla coil and
power electronics are in the center, and a ground discharge stick is on the right.
(Requires Windows Media Player)
Schematics and Electrical Design
The following schematics are the final design of my Solid State Tesla Coil. (Requires Adobe Acrobat 5.0)
The following picture shows the Tesla Coil Driver Board. To the top of the board (closet to the coil) contains the H-Bridge Power Circuit and to the
bottom is the PWM Control Circuit. The two coils in the center are the Gate Drive Transformers which basically isolate the H-Bridge Power Circuit
from the PWM Control Circuit. The small transformer on the left steps down 115 / 220 VAC line power down into a lower voltage which is then
rectified to provide the PWM Control Circuit voltage.
Tesla Coil Driver Board (topview)
Tesla Coil Driver Board (sideview)
Operation
I won't get into much theory on how the tesla coil works (Check out Richie Burnett's site at the bottom of this page for more detailed
information on Solid State Tesla Coil theory), but it works basically like this: 115-220 VAC is fed into the H-Bridge Driver Circuit and is
half-rectified. The PWM Control Circuit then basically chops us this half-rectified voltage at a much higher frequency on the order of
250-350 kHz depending on the resonant frequency of your coil. This Amplitude Modulated (AM) output is then fed into directly into
the primary coil where it causes the entire tesla coil to resonate thereby producing large break-out voltages at the toroid.
The following are actual waveforms captured using a Tektronix 784D Digital Oscilloscope:
This is the actual output (no load) of the H-Bridge Power Circuit. You can clearly see the typical half-rectified humps which occur
at 60 Hz intervals. The PWM Driver Circuit then "chops" us this half-rectified line voltage into the Amplitude Modulated waveform
you see above. The waveform is modulated at approximately 275 kHz.
The waveform shown above is a few pulses of the Amplitude Modulated output waveform at no-load.
The waveform shown above is again a few pulses of the Amplitude Modulated output waveform but this time with the H-Bridge
Power Circuit actually powering the Tesla Coil.
Operating Pictures
The following pictures were taken of the operating Tesla Coil using my new Canon D60 Digital SLR camera. I must say that it is very
difficult to capture good photos of the Tesla Coil in operation and that the photos below are a very poor representation of how the
tesla coil actually looks like during operation.
Standard Corona Discharge
Multiple arcs captured (through time lapsed photography - 10ms) discharging the toroid via a grounding rod.
More corona discharge and hot arcing to the grounding rod.
Classical Tesla Coil demonstration showing a flourescent light bulb being lit by the operating RF fields.
Solid State Tesla Coil Links
Two sites in general that provided me with lots of info on solid state coils are the following:
http://www.richieburnett.co.uk/sstate.html Richie Burnett's Solid State Coil Page (Great info and theory)
http://hot-streamer.com/hilo90mhz/tesla/sstc/SSTC.htm Chester's Solid State Coil Page
Additional Photos
(Click image for larger picture)
Completed Tesla Coil Photos
Prototype State Tesla Coil Photos
Logo, photos and original text are Copyright © 2003 by Eastern Voltage Research Corp.
All Rights Reserved. © 2003 Christopher Hill Web Master.
Last modified October 23, 2003 11:51:59 PM