Project THOR

In the beginning of the year 1999, I have started a project at the Helsinki University of Technology, High Voltage Laboratory, which has been eventually named "Thor". This project constitutes the thesis of my postgraduate studies for the degree of Licentiate in Technology. The aim of the project is to design and build a medium-sized Tesla Coil (named Thor too) suitable to perform accurate measurements and research work in general. The task is, therefore, to minimize the number of stochastic and unknown parameters influencing the device functionality. The results of this projects are supposed to facilitate the design and construction of other Tesla Coils to be used for testing of insulating materials, generation of high-voltage pulses, research on natural lightning, and other purposes. Thor is fed by a stabilized DC power supply, which is required to output 20 kV at 5 kW. As the price of commercially available power supplies with these capabilities exceeds easily $30000, this projects includes also the design and practical construction of such a device. For a description of the design criteria that led to the selection of the Tesla transformer topology and size, the power supply topology and the spark gap type, please read the Design Guidelines.

Project history and status

• January 1999: project started
• April 1999: CCPS switcher design chosen for the power supply
• July 1999: power supply prototype ready and functional (up to 5 kV)
• September 1999: power supply engineering design ready (includes PCBs and 19" rack housing)
• November 1999: power supply housed in a 19" rack, all boards have PCB
• December 1999: power supply tested up to 10 kV. Works fine, but the TC "bangs" damage very often the IGBT driver chip
• January 2000: IGBT driver chip protection resistor added. The chips now survive but the IGBTs will still be damaged during he TC "bangs"
• February 2000: the CCPS controller has been modified not to slice drive pulses in any occasion. Namely, that was causing big current/voltage spikes damaging the IGBTs
• March 2000: the CCPS IGBT drive voltage has been reduced to 15V, a fast current limiter cutting at 33A has been added
• Mid March 2000: the CCPS WORKS PERFECTLY. No damage after several 1-2 minutes runs with my old TC!
• April 2000: completed the 70 kg secondary. 50 kg of plastic + 20 kg of copper
• May 2000: upgraded the CCPS from 10 kV to 20 kV, top toroid completed, primary completed
• June 2000: primary and secondary mounted on a wheel table, top toroid mounted in place, 0.1uF 50 kV capacitor arrived the US
• October 2000: the rotating spark gap (RSG) arrived from the US
• November 2000: first light! 8.2 feet (2.5 m) streamers to ground @ 14.7 kV, 3.7 kW, 354 BPS
• January 2001: 9.84 feet (3 m) streamers to ground @ 18.3 kV, 4.3 kW, 260 BPS
• April 2001: the RSG motor has been changed and a frequency inverter has been added to control the rotating speed
• May 2001: my licentiate thesis draft is going through its first review
• June 2001: my thesis has been approved. I have got my Licentiate degree!
• Year 2002: after several measurements (and failures) I improved the original CCPS and upgraded it to revision B
• Year 2003: I designed a new board for the CCPS allowing to control the streamer growth and upgraded it to revision C
• Right now: investigating about streamer growth mechanisms...

Thor technical data	Thor related links
Power supply voltage variable from 0 to 20 kV DC power 5 kW (i.e. 5 kJ/s) pulse rate up to 500 Hz Primary capacitor 0.0967 µF inductance 99.1 µH (max) Secondary height 150 cm diameter 40 cm inductance 80.2 mH (DC) capacitance 74.4 pF* Top terminal shape toroid outer diameter 150 cm cross section 20 cm capacitance 57 pF** Spark gap type Rotating, 4 gaps in series Resonance frequency with top load 65.56 kHz Output voltage simulated 600 kV max * including the top terminal capacitance ** approximate	Power supply design Thor pictures Thor discharge pictures Primary circuit measurements Secondary circuit measurements Secondary circuit waveforms Simulation of Thor's primary and secondary circuits My licentiate thesis (PDF file, 2124 kB)

About the degree of Licentiate in Technology (adapted from the Helsinki University of Technology Degree Regulations)

In studies for the degree of Licentiate in Technology, the student shall:

1) become thoroughly familiar with his or her own field of research, and able to apply scientific research methods independently and critically within the research field;
2) become familiar with areas of science and technology related to his or her own research field, and with their research and planning methods, and
3) learn about the development, social significance, environmental effects and scientific theory of the areas of science and technology related to his or her own field of research.

The extent of the Licentiate in Technology degree is 80 credits, of which the licentiate thesis constitutes 35 credits. Postgraduate studies shall be organised which:

1) are more extensive and thorough than the Master's studies in the research area of the degree programme; this is known as the major subject of the postgraduate degree (25 - 30 credits); and
2) cover at least one other research area which supports the major subject; this is known as the minor postgraduate subject (10 - 15 credits).

Teaching to support the research of the postgraduate student shall be organised, at least partly in the form of lectures and seminars.
As an additional minor subject (about 10 credits), a further subject may be selected that complements the major or minor studies.
Postgraduate studies may also include other scientific studies (0 - 10 credits).