mercury arc valve rectifier

[SavannahLion]

Without a doubt, this is added to my list of things I must witness in action before my death.

http://hackaday.com/2010/05/05/possibly-the-most-beautiful-piece-of-hardware/

My father was a serious train buff (even purchased a rail car once) and I can not believe that he and I have never come across anything remotely like this on our travels. I thought I came across some crazy stuff, but this... this pretty much puts everything rail related (or not) I've seen to shame.

[drventure]

Oh dear lord 

I..... Must.... Get..... One......of...... those........for...... my........ cab......

[Edgedamage]

Oh there is a god! That is one cool device.

[HaRuMaN]

I want it!   

[DaOld Man]

Pretty cool.
We actually used this same technique to fire transformers for automatic welding machines.
It worked a lot like an SCR, except it could handle a lot of power (480 VAC @ 300 amps).
A small current from the gate electrode to the pool of mercury, which was in the cathode "cup", would make the mercury vaporize, allowing a large current to pass from cathode to anode.
They were called ignitrons, but you could just barely see the mercury flash on the top of the tube (anode), because the whole thing was enclosed in a stainless steel jacket.
We had to run water through the jacket to keep them cool.
http://www.rell.com/Pages/Product-End-Category.aspx?productCategory=10253

But, mind you, this was in the early 80's. I figured they were obsolete now with high power triacs and scrs on the scene, plus todays environmental issues with mercury would make them undesirable.

[SavannahLion]

Pretty cool.
We actually used this same technique to fire transformers for automatic welding machines.
It worked a lot like an SCR, except it could handle a lot of power (480 VAC @ 300 amps).
A small current from the gate electrode to the pool of mercury, which was in the cathode "cup", would make the mercury vaporize, allowing a large current to pass from cathode to anode.
They were called ignitrons, but you could just barely see the mercury flash on the top of the tube (anode), because the whole thing was enclosed in a stainless steel jacket.
We had to run water through the jacket to keep them cool.
http://www.rell.com/Pages/Product-End-Category.aspx?productCategory=10253

But, mind you, this was in the early 80's. I figured they were obsolete now with high power triacs and scrs on the scene, plus todays environmental issues with mercury would make them undesirable.

Makes sense, but it doesn't lesson the beauty of this monster any less.

According to one website, a much larger non-glass(?) version is mentioned. In a nut shell, it describes a big honking steel box that required a vacuum pump to occasionally extract any air inside. This would blow off a small amount of gassed(?) mercury into the atmosphere.

I love this kind of old technology. It's why I love the old arcade cabs. It's why I'm not a strict believer in giving up a particular avenue of technology (eg this thing) in favor of another. It's not about the money or the environment, it's about the knowledge.

I had the schematic to a portion of an arcade PCB (can't remember which now) that I brought down to the local electronics shop for advice. Most of the circuit consisted of TTL ICs. Imagine my sheer disappointment when they told me that the circuit wouldn't work but would likely blow up in my face. These guys were so deep into CMOS IC design mentality they couldn't conceive of anything otherwise. Took a tube radio grognard to work out the circuit logic and explain the experienced staff how it worked.

That's what's being lost when this kind of old technology is discarded.