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Post by vjaska on Jul 17, 2014 1:30:05 GMT
I'm 'Thunderstruck' by your answer lol. Erm sucking eggs? I don't quite follow?
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Post by Deleted on Jul 17, 2014 3:04:41 GMT
I'm a buses person, not a train person. Reading these last couple of pages I'm utterly confused. I don't really understand anything. Could someone explain? Eg, what's AC and DC? What's third rail? What's a pantograph? What's SWT? And where did the C stock used to operate? AC/DC is a form of current used by trains to draw power (AC/DC is also a band) Third Rail is what is used by some trains to draw power and is normally the outside rail seperate to the tracks. A Pantograph is the other way a train draws power, this time from overhead power lines. The pantograph is the instrument you see on top of trains that touches the wires overhead. SWT is a Train Operating Company (TOC) and is an abbreviation of South West Trains (SWT) C stock is/was a type of train used last on the Circle, Hammersmirth & City and some District Line services on the London Underground. Sub Service trains use letters to identify stock, such as the new S stock and Deep Level lines use the year to identify stock such as the Victoria Line 09 stock Hope this answers your question You could always google if you are unsure! Ok, thanks, pretty much explains it. Regarding Google, I always find it easier to ask on the forum for stuff I find confusing (as a result of previous experiences...). And I do know a little about trains, and one of those things is the letter/number codes. I just wasn't sure exactly where the C stock operated (though I had a pretty good feeling of the answer).
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Post by ServerKing on Jul 17, 2014 9:08:04 GMT
Snoggle, this "lunatic scheme" has already been signed off... my timeframe may be a little off but it is definitely going ahead. SWT are reviewing stock they will scrap, anything they cannot fit a pantograph to and convert from DC to AC. I think they are already fitting some stock with new AC traction motors. Stuff like the Class 442 and 456 will go, the newer stock like the 450 Desiro's can be converted to Dual Voltage. They are looking to get rid of 3rd rail altogether as it's obsolete and inefficient... but we are still looking at years down the line... Traction motors have nothing what so ever to do with line voltage or method of delivery. You can have either AC or DC traction motors with both AC and DC line power. Besides most, if not all modern AC traction motors used on trains are 3 phase, which means even with an AC line voltage, which is clearly single phase it must first be converted to DC, then converted to 3 phase AC using a process known as phase conversion. If the line is already DC, then the conversion is just to 3 phase AC. The real issue between 3rd rail and overhead rail is the amount of power that can be delivered to the train. 3rd rail has voltage limitations due to its relative closeness to the ground, which in turn limits current available to run the train. This in turn means has an effect on the conductor size required to deliver the power and the number of substations required to feed the line. DC overhead also has some of these limitations too might I add. With higher speeds and air-conditioning the power demands on modern trains are significantly higher than what they were even say 20 years ago. This is were AC, specially at high voltage (25KV) comes into its own. Being high above the ground the voltage can be higher, which in turn means the size of the cable supported by the catenary can be smaller, which in turn means lighter support systems, whilst still delivering the required power. Substation spacing can also be significantly reduced. When it comes to the actual rolling stock, the biggest issue in converting to dual voltage is finding space to fit the equipment required to support both voltages. The class 450 has been designed to be capable and has space for the pantograph and the necessary electrical gear to support dual voltage operation. The 442's and 456 different story, much harder to convert and probably not even financially viable. Your partially right about 3rd rail being obsolete and inefficient, though you should probably qualify that by saying on heavy rail mainline style trains for the reason that 3rd rail cannot operate at a high enough voltage to supply modern trains with a reasonable amount of sub-stations, and of course the safety aspects of exposed 3rd rail in isolated areas. In a metro environment 3rd rail it is still very much in vogue, though of course modern systems generally use protected 3rd rail systems whereby the rail head is protected and the shoes collect from the underside and of course the power demands are no where near as great as what they would be for fullsized mainline trains. I think with SWT the main issue is with leaf mulch in the autumn, ice and snow in the winter, and the amount of power actually needed, most of the energy is lost through heat. Although it's been a tried and tested technology since the 1920's, I think Network Rail see it as obsolete for a main line system, which it is. For the Underground, it is ideal, but I think also with 3rd rail, the maximum speed ever is 100 mph (I believe the fastest ever speed was 107mph, achieved by a Class 442, but don't quote me). Part of this 'Electric Spine' from Basingstoke to Southampton will shave the time off the journey, but it is also a test bed to see if they will wire up to Waterloo eventually. Obviously this will be at some expense and disadvantage i.e raising bridges, installing more feeder stations for the power, possibility of overhead line damage / sag in summer due to heat, though modern tensioning will take care of that... The issue of rolling stock will be something, unless SWT can have some dual-voltage stock from Southern when it becomes part of GTN (or the new TSGN franchise) and they get their new Class 700's. It's all hypothetical so we'll have to wait and see. Wondering if after Crossrail the wires will reach to Abbeywood or would they use dual-voltage and switch to 3rd rail at some point?
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Post by snoggle on Jul 17, 2014 19:31:43 GMT
The issue of rolling stock will be something, unless SWT can have some dual-voltage stock from Southern when it becomes part of GTN (or the new TSGN franchise) and they get their new Class 700's. It's all hypothetical so we'll have to wait and see. Wondering if after Crossrail the wires will reach to Abbeywood or would they use dual-voltage and switch to 3rd rail at some point? I don't think SWT are due any brand new stock. I've seen a suggestion recently that some more 455s might move from Southern to SWT to strengthen inner commuter routes. No idea if that has any real substance to it. Crossrail is entirely 25kv ac overhead including to Abbey Wood and the class 345s will only be pantograph equipped. I don't know if they will have passive provision to run on dc third rail. Crossrail's open air alignment from Plumstead to Abbey Wood is entirely separate from the South Eastern tracks.
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Post by ServerKing on Jul 17, 2014 23:23:14 GMT
The issue of rolling stock will be something, unless SWT can have some dual-voltage stock from Southern when it becomes part of GTN (or the new TSGN franchise) and they get their new Class 700's. It's all hypothetical so we'll have to wait and see. Wondering if after Crossrail the wires will reach to Abbeywood or would they use dual-voltage and switch to 3rd rail at some point? I don't think SWT are due any brand new stock. I've seen a suggestion recently that some more 455s might move from Southern to SWT to strengthen inner commuter routes. No idea if that has any real substance to it. Crossrail is entirely 25kv ac overhead including to Abbey Wood and the class 345s will only be pantograph equipped. I don't know if they will have passive provision to run on dc third rail. Crossrail's open air alignment from Plumstead to Abbey Wood is entirely separate from the South Eastern tracks. , I guess some of the Desiros can be converted to AC or dual voltage if they add a pantograph and they can use the wires from Basingstoke down to Southampton. I doubt they will leave the 3rd rail down, they will no doubt rip it up... interesting times, let's see if this conjecture becomes reality soon
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Post by ServerKing on Jul 17, 2014 23:29:51 GMT
I'm a buses person, not a train person. Reading these last couple of pages I'm utterly confused. I don't really understand anything. Could someone explain? Eg, what's AC and DC? What's third rail? What's a pantograph? What's SWT? And where did the C stock used to operate? Sub Service trains use letters to identify stock, such as the new S stock yeah the Underground is kind of sub-service, especially when stuck in a tunnel in the heat at least more air conditioned trains are slowly getting onto the District Line
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Post by ajw on Jul 19, 2014 1:18:18 GMT
AC/DC is a form of current used by trains to draw power (AC/DC is also a band) At the risk of being called a pedant, AC/DC is a form of current, but trains don't drawer power from it as such. Power is derived from a combination of current and voltage, AC and DC are just terms for different methods of delivering current. In fact the calculation for power is voltage divided by current. The main difference between the two is with DC the electrons in the wire only run in one direction, hence DC=Direction current, in AC they alternate hence AC=alternating current. Why you choose one over the other is a science in itself and one when I did my electronic engineering associate diploma I avoided (going the microprocessor path instead). But from a railways and power to the home perspective AC is the far greater choice, and with railways the higher the voltage the better because you then need smaller current, which in turn means small sized cables and higher voltage can go further so substations can be futher apart. Below is a table that shows the Eurostar's power capability: 12.2 MW (16,400 hp) (25 kV) 5.7 MW (7,600 hp) (3000 V) 3.4 MW (4,600 hp) (750 V) What it shows is on HS1 and in France where the overhead is 25KV AC the maximum amount of power the train can draw is 12.2MW, this equates to 488amps. The current (or amps) then dictates the size of the overhead cable required to supply this power. In Belgium, which is 3000V DC, the overhead line is not capable of delivering as much current as it can at 25KV so the maximum power it can draw is only 5.7MW, which is 1900 amps. Lastly, not that it does it any more (and in fact I had though the shoes had been removed) in Britain on the 3rd rail system which is 750v DC it can only draw 3.4MW which equates to 4533 amps. You could of course design a DC system to deliver 12.2MW of power at 3000V DC, but the size of the conductor required would be massive. Think of hanging a cable the size of a 3rd rail from the overhead . Actually Madrid metro does do something like this but for other reasons. As for 750V DC you would require 16266 amps to deliver 12.2MW. This would require a massive conductor, and even if you could get one economical there is no way in the world you could carry that much current so close to the ground. It would constantly arch out.
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Post by vjaska on Jul 19, 2014 5:56:20 GMT
AC/DC is a form of current used by trains to draw power (AC/DC is also a band) At the risk of being called a pedant, AC/DC is a form of current, but trains don't drawer power from it as such. Power is derived from a combination of current and voltage, AC and DC are just terms for different methods of delivering current. In fact the calculation for power is voltage divided by current. The main difference between the two is with DC the electrons in the wire only run in one direction, hence DC=Direction current, in AC they alternate hence AC=alternating current. Why you choose one over the other is a science in itself and one when I did my electronic engineering associate diploma I avoided (going the microprocessor path instead). But from a railways and power to the home perspective AC is the far greater choice, and with railways the higher the voltage the better because you then need smaller current, which in turn means small sized cables and higher voltage can go further so substations can be futher apart. Below is a table that shows the Eurostar's power capability: 12.2 MW (16,400 hp) (25 kV) 5.7 MW (7,600 hp) (3000 V) 3.4 MW (4,600 hp) (750 V) What it shows is on HS1 and in France where the overhead is 25KV AC the maximum amount of power the train can draw is 12.2MW, this equates to 488amps. The current (or amps) then dictates the size of the overhead cable required to supply this power. In Belgium, which is 3000V DC, the overhead line is not capable of delivering as much current as it can at 25KV so the maximum power it can draw is only 5.7MW, which is 1900 amps. Lastly, not that it does it any more (and in fact I had though the shoes had been removed) in Britain on the 3rd rail system which is 750v DC it can only draw 3.4MW which equates to 4533 amps. You could of course design a DC system to deliver 12.2MW of power at 3000V DC, but the size of the conductor required would be massive. Think of hanging a cable the size of a 3rd rail from the overhead . Actually Madrid metro does do something like this but for other reasons. As for 750V DC you would require 16266 amps to deliver 12.2MW. This would require a massive conductor, and even if you could get one economical there is no way in the world you could carry that much current so close to the ground. It would constantly arch out. I never posted the above so why are you quoting me?
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Post by ajw on Jul 19, 2014 6:46:47 GMT
I never posted the above so why are you quoting me? Fixed, I take it you have never made a mistake when removing multiple embedded quotes? Maybe I should do what everyone else does and just keep embedded quotes and make the board hard to read rather than just extracting the one sentence that I was addressing.
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