I have recently built a flyback transformer driver with a 555 timer, and have been drawing electric arcs. But I noticed that the cathode electrode(the HV pin on the transformer) heats up a lot more than the anode(the HV cable on top of the transformer). I noticed this because if I use thin cables as electrodes, the cathode starts melting and getting red hot a lot faster than the other electrode. My question is why does this happen. Thanks
Electronic – Why does the cathode heat up more than the anode in an electric arc
archigh voltage
Related Solutions
This was a comment but the links were too long.
As well as what others have said - look up "magnetic blowout" and be suitably amazed. More for DC but certainly not only. A magnet is used to deflect the arc so it lengthens and fails
Equipped in even very small and common switching devices. Many of these and these
Even Tesla did it :-)
Interest only - from here
EXPERIMENTS WITH ALTERNATE CURRENTS OF HIGH POTENTIAL AND HIGH FREQUENCY.
BY NIKOLA TESLA.
A LECTURE DELIVERED BEFORE THE INSTITUTION OF ELECTRICAL ENGINEERS, LONDON.
With a Portrait and Biographical Sketch of the Author.
NEW YORK: 1892
MOSFETs are sensitive to voltages exceeding their ratings.
When you switch off the device, the inductive coil is very likely to have generated an inductive back-EMF of voltage high enough to damage the MOSFETs. After all, the electrical energy stored in an inductor has to get out of somewhere - When you power off, the energy finds some path or the other to discharge itself, and resultant voltages can be considerably higher than the original voltage across the inductor.
A generic fix for inductor back-EMF woes is to apply a reversed diode across the coil, or in this case, possibly across the MOSFETs. Do not depend on the body diode of the MOSFETs to provide a discharge path, as body diodes rarely have suitable characteristics to serve as a high energy discharge path.
Related Topic
- Circuit building question
- Electronic – Does magnetism affect the likelihood of an electrical arc occurring
- Electronic – Light bulb burns out — why there is an arc in the switch
- Electronic – Why does only the tip of the electrode melt when arc welding
- Electronic – Why are overhead electric wires allowed to have higher voltages than third rails for rapid transit railways
- Electronic – the resistance of an electric arc between two graphite electrodes
Best Answer
In an electric arc, electrons are being stripped from their atoms in the air & fired with high energy towards the anode.
Some of the electrons are fired from the cathode directly, and others are stripped from air atoms, but eventually, if the plasma is sustaining, they end up striking the anode.
Meanwhile, the much larger & denser necleii of the electron-stripped atoms are not drawn through the arc with as much speed, any many end up dissipating into the surrounding gas, rather than impacting the cathode.
Due to this imbalance in the impacts of energetic particles, the vast majority of arc-caused heating to the electrodes occurs on the anode.
For more explanation, here is a detailed and informative article from lincolnelectric.com, explaining some of the various properties & arrangements of this tranferrance which are exploited in the verious metal arc-welding processes.