This is in regards to a thumper that followed me home last week. A thumper is a machine that makes high voltage capacitor discharges of thousands of joules, to find faults in underground buried cable. Mine is designed to deliver up to 4,062 joules, or approximately the energy carried by bullets from a burst of assault rifle fire.
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Today, a local luminary in the field of coin shrinking, Lichtenstein figures, and other fun high voltage things visited me and my thumper machine. I am not mentioning his name out of respect for his privacy, and feel very highly about him.
Anyway.
After I dragged its two pieces into my garage, we looked at the machine and opened up the covers. Some interesting things came to light.
- It was a 25 kV DC machine, with two contactors: a safety grounding contactor to ground the caps when power is off, and the thumping contactor to connect capacitors to output cable.
2.It has a variac for varying output voltage of the high voltage transformer. The high voltage is rectified by a center tapped rectifier (two diodes).
- It has a limiter arrow on the voltage display that causes the output contactor to close when capacitor voltage reaches the limiter.
- It also has a DISCHARGE button that can cause the discharge contactor to close at operator request.
- My machine did not work because the limiter (whose purpose I did not understand) was set to zero.
After he left, I wired up the machine and tried to use it. I made a primitive spark gap out of two large copper pieces. As it turned out, it works great. It charges the caps and when it reaches the preset voltage, it discharges into a spark gap.I only tried it at up to 10 kV.
Its output of 4k joules is supposed to be enough to shrink coins.
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