Save a piece of electrical history! Mercury arc rectifiers under threat

[Lucien Nunes]

The Laxey substation of the Manx Electric Railway is one of the last mercury arc rectifier installations in the UK to have been doing its original job on its original site. There are very few left at all, let alone a complete working station. Now decommissioned, its survival is in the balance and we need support for this great old piece of British engineering before the powers that be decide to scrap it, as has been threatened. Engineers and non-technical people alike have been fascinated by the mercury arc for nearly a century - please sign the petition before next week's meeting to help ensure that such a great example is saved for future generations to learn from and admire:

Save the Laxey Manx Electric Railway Mercury Arc Rectifier Sub Station Petition

If you're interested in the technicalities of mercury arcs, there's a page about one of mine here:

Electrokinetica - Mercury arcs: Nevelin

Cheers
Lucien

 

[GLENNSPARK]

This may be a bit naive, but what is it?

here:

 

[Lucien Nunes]

Rectifier - converts AC to DC. Modern day equivalent would be silicon rectifiers. Mercury arcs are distant cousins of the fluorescent tube (invented by the same man, Peter Cooper Hewitt) and the radio valve. Unlike a valve rectifier the cathode is a pool of mercury, the mercury vapour giving the lowest power loss. MARs were ideally suited to the 100-500V range and 50-300A in glass bulbs and higher current in steel tank versions. Widely used for DC supplies in steelworks, tramways, any kind of DC motor installation, battery charging, cinema carbon arcs etc etc. Main competitors were motor-generators, rotary converters and metal rectifiers.

 

[Paultrim123321]

Basically, it provides rectification to an AC supply and converts it into DC.

 

[GLENNSPARK]

it works on the principle that mercury will only conduct in one direction....

 

[Carlosfandango]

I guess a quick Google search might have done the same, very interesting though.

 

[electron1]

I remember MARs being used in Power Stations to supply Electrostatic Precipitators.

 

[Carlosfandango]

What voltage is the AC input?
I have no knowledge in DC at all!!

 

[Silly Sausage]

I know a very good source of info for MARs, not allowed to post a link though! :smilielol5:

 

[Lucien Nunes]

to supply Electrostatic Precipitators

Aaaaah, when you say that I think of rotary mechanical HV rectifiers. Pleeease tell me there's one of these beasts left to save!

What voltage is the AC input

Normally in the 100-500V range for glass bulb types. But there were HV versions that looked rather different, such as were used on the HVDC transmission systems. In principle you can use mercury for any voltage, its minimum forward drop is about 14V though so anything below 75-100V starts to get rather inefficient and an M-G set or oxide rec was better.

 

[Knobhead]

As an apprentice I was fascinated by the Mercury Arc Rectifiers we had. Unfortunately scrapped along with the open slate switch gear. OK the switch gear was a bit iffy, you’re hand went between the +ve and –ve arc chutes when closing the ACB’s.

This was their boring replacement:

 

[GLENNSPARK]

here:

Mercury Arc Rectifier - YouTube

Mercury Arc Rectifier - Manx Electric Railway - Laxey I.O.M. - YouTube

 

[GLENNSPARK]

1908 Car Battery Charger with Mercury Arc Rectifier - YouTube

Mercury Vapour Rectifier - YouTube

 

[GLENNSPARK]

Mercury Arc Rectifiers, a brief overview - YouTube

Mercury Arc Rectifier - YouTube

 

[Lucien Nunes]

Thanks to everyone who has signed so far, if you fancy writing to Graham Cregeen, the minister who would be able to leverage this project, to add your support, you can find his contact details here:
Tynwald - Parliament of the Isle of Man - CREGEEN Graham Derek, MHK
Cheers
Lucien