Would a sealed power relay filled with an inert gas like argon last a long time? - Page 1
Forum section: electronics / beginners

author: incf
author_rank: Frequent Contributor
timestamp: April 21, 2025, 01:23:38 am
content: Silver based contacts used on power relays have some awful properties with regards to oxidation/contamination/etc. Especially if they sit idle too long.Would a sealed ~40A power relay (using silver contacts) filled with an inert gas like argon last a long time?or are there practical issues? (deposition of metal vapor everywhere inside of the relay?)Relays are often outfitted with vents for some reason.

author: TERRA Operative
author_rank: Super Contributor
timestamp: April 21, 2025, 02:23:22 am
content: X-rays from arcing when switching heavy loads?

author: calzap
author_rank: Frequent Contributor
timestamp: April 21, 2025, 06:05:22 am
content: Contacts of a sealed, encased relay filled with argon should last longer than in a relay exposed to air but maybe not that much longer. An arc is destructive to metal even in an inert atmosphere. Argon is used as a shielding gas for some types of arc welding … and yeah, the metal melts.Relay cases are probably vented for multiple reasons … equalize changes in barometric pressure, allow heated air to escape when the relay is very active (and back in when it’s quiet again), allow any condensation to evaporate, etc.Mike

author: coppercone2
author_rank: Super Contributor
timestamp: April 21, 2025, 06:20:01 am
content: vented relays last longer and argon is not just used as a shield gas, it has to do with the arc. It should get destroyed quicker with argon. I think you want nitrogen, but it would always be better to let the arc gasses vent out, so long nothing bad gets in there. I think a open one in a nitrogen filled box would work best.If you seal it with nitrogen, perhaps you don't get corrosive ozone forming. But I don't know about the vaporized metal being confined in there.it has to do with the work function and the gas ionization potential, once the arc is made some gases sustain them longer. Good for welding, bad for relaysargon helps the welder keep an arc going longer / easier / steadyNot sure it matters for closing (because its mechanically quenched), but for opening... you will get longer arcs drawn in argon then air or N2. I think its a very complicated problem to understand, because there are many factors that have to be evaluated. The arc temperature, arc duration, plasma chemical reactions, arc focusing (if you weld you know you can get a diffuse or point arc), arc cooling rate (does it get cooled by the thermal conductivity of the gas? not sure), arc wander

author: incf
author_rank: Frequent Contributor
timestamp: April 22, 2025, 09:03:04 pm
content: Quote from: TERRA Operative on April 21, 2025, 02:23:22 amIs that really a thing? Does it depend on the pressure of the gas?I thought only vacuum tubes did that (the word thermionic emission comes to mind for some reason).

author: TimFox
author_rank: Super Contributor
timestamp: April 22, 2025, 09:22:37 pm
content: Quote from: incf on April 22, 2025, 09:03:04 pmRoentgen discovered x rays in 1895 using "Crooke's tubes", which are gas-discharge tubes: the pressure (partial vacuum) and length of the tube determined the voltage across it (like in a "VR tube"), following Paschen's Law.Electrical generation of x rays comes from Bremsstrahlung ("braking radiation"), where the electrons decelerate suddenly when hitting the anode. The gas outside the anode has little effect on the process.(A visiting German professor giving a guest lecture at my university asked a local student who spoke good German to sit in the front row, in case he had a problem with English. The professor asked "Wie sagt man 'Bremsstrahlung' auf Englisch?, to which the student replied "Bremsstrahlung".)

author: amyk
author_rank: Super Contributor
timestamp: April 22, 2025, 09:47:26 pm
content: For very high power,https://en.wikipedia.org/wiki/Sulfur_hexafluoride_circuit_breakerare used.

author: calzap
author_rank: Frequent Contributor
timestamp: April 23, 2025, 02:11:19 am
content: X-rays from bombarding a target with electrons are of 2 sorts. Characteristic x-rays are emitted when an electron is knocked from an inner atomic orbital and the orbital is refilled from a more outward orbital. The highest energy characteristic x-rays come from refilling the inmost orbital of uranium, and their energy is 116 keV. Bremsstrahlung are high energy photons that result when traveling free electrons (i.e. non-orbital electrons) have their course changed. The only limit on bremsstrahlung energy is the energy of the bombarding electrons.Mike

author: Andy Chee
author_rank: Super Contributor
timestamp: April 25, 2025, 04:33:22 am
content: Don’t forget to wear your arc flash protectionhttps://youtube.com/watch?v=U1LEhgwF3Zg