The power supply to be constructed within the Thor project is not a stabilized DC voltage source but can the better described as a Capacitor Charging Power Supply (usually referred to as CCPS in technical literature): the capacitor to be charged is the one in the Tesla Coil primary circuit. A charging cycle begins after a triggering signal pulse is given: when the voltage on the capacitor reaches a predefined value, the CCPS goes into an off-state, waiting for the next trigger pulse.
A switching power supply is employed, using four IGBTs connected as full-bridge. The series resonant load topology is particularly suitable for capacitor charging because it behaves as a constant current source: charging time is thus boosted and no special precautions are needed to limit current surges at the beginning of the charging cycle. Additionally, by properly matching resonance and switching frequencies, the IGBTs close and open at zero-voltage and zero-current time, therefore minimizing switching losses.
For a basic description of the power supply topology, operation and benefits, please read the Series Load Resonant Power Supply basics page.
The power supply design is modular and composed by the following blocks:
The voltages provided by the four transformers are individually rectified by a 7 kV 3 A diode bridge and then connected in series to provide 20 kV 5 kW total. The resulting voltage is used to charge the primary capacitor to a rate of 500 charges/s maximum.
Design of a 20 kV, 5kW Capacitor-Charging Power Supply (zipped Word document, 806 kB)
Design of a 20 kV, 5kW Series-loaded Resonant Power Converter (zipped Word document, 1030 kB)
The rack prototype, with 1 DRIVER module and 2 TRANSFORMER modules
One TRANSFORMER module
One DRIVER module
A small sample of all IGBTs I have destroyed
The 19" power supply rack (planned)