The Tesla coil to rival all Tesla coils! A souped up version of the famed QCWDRSSTC. The design goal of this system is 10 foot sword like sparks using water cooled interleaved inverters powered by a 25Kw class D delta modulator. This is a joint project between myself (Eric Goodchild) and my good friend Steven Caton.
This page will serve as the documentation, progress will be updated on this page.
11/11/11 - The concept of the hog is formed and the decision to construct the device is made. We set the initial design goals for the project in that it had to make 10 foot sword like sparks, was to be water cooled and have a fres of ~400KHz.
12/18/11 - Steve and myself decide to split up parts of the project to better construct it. Steve will be building the water cooled H bridges and current sharing transformers. I will be building the class D delta modulator that will modulate the inputs to the H bridges.
12/20/11 - While dropping off our two large DRSSTC in AZ for WWT, we talked with Chris and Henry about the design. Chris offered a secondary from one of is old projects the quadzilla quad 833C VTTC. The secondary is wound with 18 AWG wire and has a fres of about 420KHz (without a top load) and has an uncountable number of coats of secondary varnish. The secondary it's self is a work of art, it will be a tall order to make the rest of the coil worthy of the secondary!
3/5/12 - Steve finished constructing one of the water cooled H bridges at the UCLA plasma physics lab. We are currently only building one bridge to test the IXYN82N120C3H1 IGBTs at the frequency of the secondary LC circuit (~400KHz). We thought about using the IXYS 60N60 IGBT's first but decided not to because of there low 600V rating. The 82N120 have about the same speed and current rating as the 60N60s but have a 1200V rating significantly cutting down on the length of the PW that would have been required to make 10 foot sword like sparks. The bridges are built on a 1" thick copper water block with a 9/16" water channel.
7/7/12- A major step in the HOG has been reached, the completion of the primary coil. It is 3/8 copper tube 12 turns. The base is made out of polycarb sheets. It also sports a 5/8 strike rail.
7/8/12 - We decided on a steel base because of how much this coil will weigh when complete. The base was made using 1x1 16 gauge steel square tube. Base was MIG welded together.
7/18/12 - After much deliberation we have made a major design change to the system rather than using a dedicated modulator to control the input voltage to the bridge we are switching to a ZVS phase shift full bridge. There are a couple reasons for this, firstly it cuts down on a lot of the hardware that will be needed (2 IGBTs, large inductor cores, controller, etc...) This reduces the complexity and increases efficiency.
We have also opted to use 8 full bridges of transistors to drive the HOG, two bridges per water block (one on each side). This is based on there 100A rating and that fact that we plan for a max current around ~800Apk Each bridge will be linked with current sharing transformers so that they all share current evenly. A added bonus is that they will also be galvanically isolated from each other protecting the other bridges in the event that one fails.
Here are the 4 bridges and out proposed bus layout for the many capacitors.
Stay tuned there is more to come!