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Registered Member #2422
Joined: Tue Oct 06 2009, 02:41AM
Location:
Posts: 85
My idea: To use high frequency saturable reactors (like the one described here) one each in series with the secondary and primary coil to vary the total inductance of the circuits? The resonant frequency could then be adjusted by a separate DC circuit.
Is this possible/practical?
I suppose the difficult part would be getting magnetic isolation between the control coils and the main coils. Would a faraday cage / metal box work?
Registered Member #135
Joined: Sat Feb 11 2006, 12:06AM
Location: Anywhere is fine
Posts: 1735
You could if you want, but the first thing you should know about this is that every inch of coil extra, and every extra uH is wasting power that's not being delivered into a primary of a Tesla Coil.
Now if your not intending on using this for a Tesla coil, then it may not matter.
Tesla himself used an external roller inductor which you can sometimes see in his setups, which he remarked that he was probably losing up to 40% of his power through this extra inductance.
Registered Member #1232
Joined: Wed Jan 16 2008, 10:53PM
Location: Doon tha Toon!
Posts: 881
I think something like the variometer arrangement is a far better way to adjust inductance at high power as it doesn't have any moving contacts.
You can also use two primary coils one above the other and connect them in series. As you adjust the spacing between them it adjusts the total inductance. As for coupling to the secondary, i'd bet that if you raise one and lower the other by just the right amount, you could decrease the primary inductance but keep the primary-to-secondary coupling the same!
That's the sort of thing I would be looking at to adjust the primary resonant frequency on the fly. Definitely not saturable reactors.
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
I think it would work fine in theory. But the adjustment range offered by the saturable reactor described in that patent is very small: it can vary from 35 to 50 ohms of reactance at 13.56MHz.
This might tune the primary somewhat, but it won't have any effect on the secondary, whose reactance is thousands to tens of thousands of ohms.
Tesla coils don't seem to need on-the-fly tuning anyway, except perhaps Class-E ones.
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resonant frequency control with a saturable reactor
