Introduction: Marx Generator With Inductors
This is a 4 stage choke charging Marx generator.
The circuit is the same as a normal marx generator, the only difference is that there are inductors instead of charging resistors. With smooth, filtered DC current the inductor acts as a simple wire, it has ohmic resistance only. In case of a very fast high voltage pulse (this occurs when the first capacitor breaks down a spark gap) the impedance of the inductor will be so high, that it will act as a high value resistor, it will block the path of the current, so the current will choose the easier way. (through the other spark gaps)
The advantage of this circuit is that there are no high resistors, only inductors, so current can flow easily through them, the charging time will be very short. This will increase the rate of fire. With a good high voltage power supply that produces significant current, this Marx generator can fire sparks with higher speed.
Step 1: Components
1. Spark gaps are adjusted to 4.5 mm. This is about 10 kV. Spark gaps are made of screws and acorn nuts.
The output spark gap is 35 mm, but it can be longer. The output voltage is approximately 40 kV. Because of the sharp wire electrodes, the output spark is bigger than an electrode of acorn nut.
2. Capacitors are 4nF 20kV homemade capacitors. They are made of aluminum foil and transparency sheet. I'm not going to do deeper how to make this type of capacitors, you can find a lot of video about aluminum foil capacitors, but it's important that I used 5 layers of transparency seet between the aluminum foils to endure 20 kV. Capacitance is not critical, more capacitance will increase charge, and produce brigther, louder sparks.
3. Coils are made of cardboard tubes, 27 mm diameter. 210 turns of 0.16 mm (34 AWG) magnet wire. The length of winding is 47 mm. The coils and cardboard tubes are coated with varnish. Inductance is 540 uH. Inductance is not critical. I think it must be somewhere between 400 and 600uH.
4. I use a low value charging resistor to increase firing rate. It's 500 kΩ, made of four 2 MΩ resistors in parallel. Don't go below 500 kΩ.
5. I use protection chokes between the power supply and the Marx generator in order to protect my flyback and ZVS driver from high voltage spikes. They are 60 turns of 0.5 mm (24 AWG) wire on the same diameter cardboard tube (27 mm). Inductance is not critical. (later, I added two small ferrite toroids with 3 turns to improve protection)
Input voltage of the Marx generator is 18-20 kV fom a DC flyback transformer, driven by a ZVS driver. It's input voltage is 30V.
Step 2: Assembly
I made the frame for this generator from bakelite sheets. It's vertical layout.
The layout can be varied, it can be horizontal, it can be build on a bench too, ( be careful, wood can absorb humidity use varnish to protect wood) the coils can be built horizontally and vertically too.
Capacitors can be replaced by glass Leyden jars. They have excellent dielectric strength and dielectric breakdown will not damage them so much as plastic dielectric ones.
I advise you to use plastic covered wires between capacitors, coils and spark gaps and cover all sharp edges, soldering, connections with epoxy or paraffin wax ( I used this one) in order to avoid corona discharges that cause efficiency loss.