Talk:Mercury-arc valve

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Clarity[edit]

This article does not explain things quite well enough. The purpose of the excitation electrode is unclear. A simple circuit diagram that includes the anodes, cathode, and excitation electrode would be enormously helpful. Benandorsqueaks 05:01, 25 December 2005 (UTC)

I've tried cleaning up this article a bit but I've got to hit the books on this one. I hope Mr. Deutsche-Volt will lay off the poor translations for a while. --Alexwcovington (talk) 21:43, 28 Mar 2005 (UTC)

Whew. Agreed. There's whole paragraphs here that are baffling. I'll have a hack or two at cleaning this up - it's worth having this because most of the HVDC project articles refer to mercury arc valves. --Wtshymanski 17:33, 29 Mar 2005 (UTC)

Notes[edit]

I've got to track down a description of the glass and metal envelope forms, since the article is vague. I found a picture in "Standard Handbook for Electrical Engineers" which I may try to redraw. I don't think a thyratron is a mercury-arc device - it doesn't have a pool cathode at any rate. Triggering is important and not discussed yet. I've *seen* the glass-bulb form but I don't think those have been used since before WWII. A discussion of why solid-state devices replaced the arc valves is in order. Flashback is a problem to be mentioned, as well as cooling requirements. Mercury valves were developed by GE and Simens as well as ABB - needs references. --Wtshymanski 18:09, 29 Mar 2005 (UTC)

A thyratron can be either a cold cathode device with a pool of mercury, or a heated (thermionic) cathode device without a pool of mercury. The latter can be either a mercury arc or a mercury discharge device. 20.133.0.13 13:54, 14 March 2007 (UTC)
An ignitron uses a pool of mercury, not a thyratron. Thyratrons can use mercury vapor (a small droplet of mercury being the source), but often use other gases such as hydrogen, xenon, deuterium. A thyratron can use either a cold or a heated cathode, but modern thyratrons use heated cathodes exclusively. Bert 14:03, 15 March 2007 (UTC)

Picture trouble[edit]

WHen I click on the picture I uploaded for the article, I can't see it, only it's description page. What did I do wrong and how do I fix it? --Wtshymanski 03:27, 4 Apr 2005 (UTC)

Legacy DC power grids[edit]

Static inverter stations were used to provide DC power to legacy Edison style DC power grids in urban centers until the 1950's. These were in use in Helsinki until about 1950 and in the UK even longer. Who knows more about this? -- Petri Krohn 06:45, 10 January 2006 (UTC)

The UK had a DC link scheme between Kingsnorth power station on the Isle of Grain in Kent and Beddington in South London and Willesden in North London. There were 3 converter stations and the Kingsnorth station used controlled mercury valves to rectify the generator output into plus and minus 266 kV DC. The positive pole fed the Beddington station which used identical valves but operating as inverters. The negative pole similarly fed Willesden. The scheme also allowed Beddington or Willesden to operate as rectifiers and feed power to the other, but such operation was never required. The scheme was still operational in the early 1980's, but is no longer in operation. 20.133.0.14 13:52, 14 March 2007 (UTC)

Explosion hazard[edit]

I'd like to see a valid reference for the "double layer explosion hazard" - unfortunately I can't tell if this is just advanced plasma physics beyond my ken or absolute pseudoscience. A Google search was very dishearting, only producing a couple of astrophysics papers. In all my years of reading about HVDC systems I've never seen any reference to "explosions" as a particular hazard of mercury arc rectifiers, and the Wikipedia is the only place I've found this association, which makes me highly dubious. --Wtshymanski 19:56, 14 January 2007 (UTC)

You got a pair of valid references in the newer version you just reverted:
The former reference contains a brief description of the issue. The latter has a detailed description of the problematics on pages 15-16 of the PDF file. I believe the phenomenon deserves a mention and a NASA publication has enough weight to back it. Alternatively, please explain why you labeled it as "nonsense". --Shaddack (talk) 20:00, 4 September 2010 (UTC)
Do the sources, or either one of them specifically speak of explosion hazard in mercury arc valves? -- Petri Krohn (talk) 07:37, 5 September 2010 (UTC)
It looks like the astrophysics paper hosted on the NASA domain does refer to mercury arc valves. My issue is that none of the papers on mercury arc valves refer to this astrophysics phenomenon. It seems very peripheral and irrelelvant to how these devices were used and a long dissertation here is not germane to illustrating the use and issues of mercury arc valves. Mercury arc rectifiers didn't "explode" - is this paper perhaps talknig about flashback? --Wtshymanski (talk) 13:26, 7 September 2010 (UTC)

London Underground[edit]

Mercury arc valves/rectifiers are still used on the London Underground. They were used for both traction and electric lifs.

This page shows on in use on 27th January 2000 still powering the lift of an air-raid shelter at Belsize Park London Underground Station:

http://www.subbrit.org.uk/rsg/sites/b/belsize_park/index.html

--217.18.21.2 18:31, 9 February 2007 (UTC)

There are many examples of mercury arc rectifiers still in operation, mainly in places where the cost of replacement is not considered worthwhile because the use is not intensive enough. The mercury arc rectifier, generally never wears out. 20.133.0.14 13:52, 14 March 2007 (UTC)

Others[edit]

The statement about Tungar rectifiers in the "Others" section should be clarified to indicate that these are not based on Mercury vapor, but rather Tungsten (electrodes) and Argon (gas), thus Tung-Ar.

32.97.110.142 18:15, 13 September 2007 (UTC)Dave

Noted; moved the description to the rectifier article in with the other electron tube devices. --Wtshymanski 21:07, 13 September 2007 (UTC)


Efficiency[edit]

" Before the advent of solid-state devices, mercury arc rectifiers were the most efficient form of conversion from alternating to direct current."

not by a long way. Mechanical rectifiers waste a fraction of the power, and were used in many applications before and after the invention of the mercury rectifier. 62.253.52.61 (talk) 17:47, 9 June 2008 (UTC)

Cool. Do you have a reference? Were people still buying rotary converters for DC supplies after mercury arc rectifiers came along? --Wtshymanski (talk) 21:24, 9 June 2008 (UTC)

Nice Reference[edit]

McGraw-Hill's Engineering Companion from google books --Stone (talk) 09:44, 5 March 2009 (UTC)

Properties of mercury[edit]

What properties of mercury are important for the function of this device? Is the liquid state of mercury not important for operation, only the electrical conductivity? Can the device operate lacking the electric arc?--84.232.141.38 (talk) 17:08, 12 April 2011 (UTC)

Ionization is the key bit. A mercury arc valve without an arc isn't operating, but you can have an arc without mercury. --Wtshymanski (talk) 18:09, 12 April 2011 (UTC)
How about vapour pressure of mercury? Is it important for the arc?

If there is arc without mercury, then mercury can be replaced with other metals like NaK, galinstan.--84.232.141.38 (talk) 17:14, 20 April 2011 (UTC)

That's original reserach and out of bounds for the article. Have you seen anyone actually using other metals? Certainly a "mercury free" fluourescent lamp would be a hot seller, but the fact that no-one seems to be offering this indicates it's not the melting point, but the behaviour of mercury on ionization (and the energy of the photons it gives off) that is the key property. --Wtshymanski (talk) 17:58, 20 April 2011 (UTC)
How is the ionization expressed by a quantity? If electrical conductivity is the answer (and perhaps ionization energy), then galinstan's conductivity is about three times greater than mercury's (by comparing data presented in articles). A straighforward comparation is not OR.

On the other hand galinstan is a recent development, but there must be some sources published somewhere refering to the investigation of other metals' appropiateness/suitability for the purpose discuted here. --84.232.141.38 (talk) 18:12, 1 May 2011 (UTC)

Johann Sahulka[edit]

Did the work of Johann Sahulka precede that of Peter Cooper Hewitt? Biscuittin (talk) 22:06, 2 November 2014 (UTC)