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Introduction
Having already built a medium and a small DRSSTC, I feel that I have the experience and want the challenge of building a large DRSSTC system.
Considerations
I decided to design a high impedance system to run longer on times at a lower primary peak current. The average power flowing in the primary circuit will be the same as a low impedance system, but total cost of the system will be much lower. A MMC is typically much more expensive for a low impedance coil as a large capacitance is needed to work at a resonant frequency around 40 kHz. A high impedance primary coil also have a lot more surface area and will thus not require as much cooling.
When drawing power in the term of up to 10kW, power factor will become a problem.
Specifications
| Bridge | 2x CM300DY-24H IGBTs in a full bridge configuration |
| Bridge supply | 4x 6000uF 350V filtering capacitors, two in series, two string in parallel for 6000uF at 700V. |
| Primary coil | Flat primary. |
| MMC | 0.4uF at 12kV. Made from Cornell Dubilier (CDE) 942C20P15K-F, 16 parallel strings of 6 in series. |
| Secondary coil | 315 mm diameter, 1500 mm long, 2200 windings, 0,75 mm enamelled copper wire. |
| Resonant frequency | Around 38 kHz. |
| Topload | 7 rings of 22 mm copper tubing forming a toroid. |
| Input power | |
| Spark length |
Schematic
The driver is a variation of Steve Wards universal driver
Construction
24th December 2011
Work on the secondary coil began on Christmas day and lasted until the 6th January 2012 where is had its 7th layer of varnish. The first winding rig fell apart after the 4th layer of varnish and we had to build a better one.
The winding of the secondary coil was done on the first day, in about a total of three hours. The of the time was spent on varnishing. Took 16 hours for each layer to harden before a new layer could be applied.
With the frequency converter set at 70 Hz, the gear ratio and small to large diameter gear gave a winding speed of about 0,5 m/s.
29th December 2011
The primary supports was made from acrylic from the back light panel in computer monitors. It felt somewhat different to work with than new acrylic and it is our theory that the great tensions that it saw doing milling resulted in the catastrophic cracks that eventually led to the death of these supports.
On the 7th of January 2012, we gave up using these. Many hours of work was wasted here and we are now searching for a better material for the supports.
Conclusion
N/A
Demonstration
N/A
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Amazing job you are doing. Clearly you are a details person.
Cheers