Ballasting/Current Limiting
Updated: October 29, 2004
D&M's High Voltage, DMsHV.DavMcKin@verizon.net We offer variable reactors (slide chokes) in a commercial version for this application (current limiting or ballasting tesla coils). You can see a picture of one on our website at: http://www.dmshv.com/
http://www.richieburnett.co.uk/ballast.html Some very good info.
http://www.geocities.com/nickberndsen@sbcglobal.net/ballasts.html Good stuff with photos
Terry Filter for neon sign transformers, http://hot-streamer.com/TeslaCoils/Misc/NSTFilt.jpg
Original poster: "Patrick H." This has nothing to do with the steel rod idea but it may help by giving you a ballpark figure to work with. My current limiter was made by winding about 50-60 turns of 2.5 square millimeter house wire (rated at 25amps continuous) onto an old MOT core this limits to current in my MOT bank to about 35amps. In terms of linkage http://tesla.reidconsulting.com.au/tesla.html details exactly what you're building.
Question: Slide-choke construction Original poster: "Erik B." A while back, in a post titled "the amazing variable choke," someone mentioned that they'd build themselves a slide choke, running a bundle of epoxied steel rods through a pvc form with the coil wound on it. I'm now thinking of building one myself, but the dimensions I'm a little shaky on. I have a +/-300ft roll of 10ga thhn which seems up to the challenge, but should it be wound with very few layers on a long form, or many layers on a short form? I would think that to get the most out of the rod's travel, it would have to be wound long. 5 or so coil layers over ten inches of travel sound decent?
Answers: Wind it over a length of 28 inches. Use small 1/4 x 1/4 phenolic spacers to keep each layer with a generous air pocket and then use a 100 CFM muffin fan to blast air through it. Ours is wound with #8 AWG and works great up to 16 kVA. The core we used is 2.5 x 2.5 in. square and moves approx 20 inches. Dr. Resonance, Resonance Research Corporation , E11870 Shadylane Rd., Baraboo, WI 53913
Another interesting advantage using a large sliding choke offers is that it can eliminate the costly variac altogether! With the core in full, only a few Amps (magnetizing currents) are drawn by the HV xfr so while it remains at the full 240 VAC it doesn't get any appreciable current so nothing happens. The xfr can't supply enough current to charge the caps. As the core is slowly withdrawn the current begins climbing. You can set the current point at any current level you desire and do not need a variac at all. It's an interesting concept and works very well. We use this idea to eliminate variacs in all of our larger systems. Dr. R.
