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Registered Member #2028
Joined: Mon Mar 16 2009, 08:13PM
Location: Norway
Posts: 319
Just a thought, how well would it work to replace those resistors with relays, or transistors? Would they suffer from a killer voltage spike? By using triggered spark gaps you could ensure that the gaps only fire while the relays are open.
Renesis: Each of these elements has to withstand a voltage equal to the charging voltage, V0, of each stage. So, it depends on the charging voltage range you want to use. With relays open at the discharge phase, the actual voltage difference across them will be V0.
The lesson to be learned here is that it is a mistake to have all resistors of equal value, and that the resistor values should be calculated on the need for the keep alive current of the arcs - say 5A - 10A - rather in the rather arbitary way in which values seem to be assigned in a lot of DIY Marx circuits I've seen, without concern for the time constant, or the output impedance of the erected circuit.
I think the class of elements that serves a purpose needs to be of equal value in a marx circuitry, or imbalanced voltage drops will appear at the discharge phase. Therefore, the side elements need to be of equal value, because they serve as the path to ground (tail resistors). The front resistors also need to be of the same value, in case they are implemented in each stage, but they need not be equal to the tail resistors.
ALso, if you implement front resistors, a large range of values would work fine, since an arc just needs only several mA to stay alive, and a bit less voltage difference from that, that intiated it. (I have seen that in arrangements of tens of kVolts with centimeter-gaps, that sustain the discharge, being fed from just the high voltage power supply).
Registered Member #664
Joined: Sun Apr 22 2007, 10:31PM
Location:
Posts: 13
Replacing resistors with coils like tesla coils secondaries might work well. I simulated that kind of marx generator with 200u coils and 1n capacitors and it seems to work.
Registered Member #311
Joined: Sun Mar 12 2006, 08:28PM
Location:
Posts: 253
I've experimented with inductors but you can get problems due to the resonance of the inductor with nearby capacitor, leading to transient overvoltageing of the cap - adding some damping resistance may fix this - haven't tried it myself
Registered Member #211
Joined: Sun Feb 19 2006, 05:33PM
Location:
Posts: 27
Hi guys With regards to inductive charging: Since the typical construction of the charging elements (resistors or inductors) is linear, you could wind one very long inductor with taps on some PVC pipe, that way it might save space and be easier to mount. Can anyone guess what the effect would be if you added a ferrite core common to the whole inductor? (besides increase in inductance) About ringing, what about isolating each tap with a diode?
I am looking to build a small marx bank fairly soon, I cannot find HV resistors at any reasonable price and so I am turning to try inductors!
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Different Marx Generator schematics
