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Old February 10th, 2012, 03:02 PM   #101
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I mean, in the snow, the first theing the UK could do would be heating the points, but no one seems to have bothered to implement that...
I'm 25, more than 2 inches of snow lasting more than a day in the South of England has happened about 6 times in my life - four of which in the last 4 winters (one of which is still happening). It normally melts pretty quickly, or not much falls and settles in the first place.

South London normally has the snow melt straight off the bat. The South Coast and East & North Kent normally either miss the snow, or it melts quickly.

That leaves the area in between that doesn't get much snow, but when it does it gets problems. The question of spending money on points heaters was silly 5 years ago - it was about two or three days every 7 or 8 years on average. Now it's less silly, but is still a big risk - these 4 years could easily be a short cold spell, and you buy them and snow happens rarely again as soon as we're out of it.
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Old February 11th, 2012, 01:26 AM   #102
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Originally Posted by sotonsi View Post
I'm 25, more than 2 inches of snow lasting more than a day in the South of England has happened about 6 times in my life - four of which in the last 4 winters (one of which is still happening). It normally melts pretty quickly, or not much falls and settles in the first place.

South London normally has the snow melt straight off the bat. The South Coast and East & North Kent normally either miss the snow, or it melts quickly.

That leaves the area in between that doesn't get much snow, but when it does it gets problems. The question of spending money on points heaters was silly 5 years ago - it was about two or three days every 7 or 8 years on average. Now it's less silly, but is still a big risk - these 4 years could easily be a short cold spell, and you buy them and snow happens rarely again as soon as we're out of it.
I mean, this is debating personal opinions etc etc, but nearly every year there's a 10cm + fall of snow associated with a cold snap at some point, if I remember correctly, but hey
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Old February 12th, 2012, 02:35 PM   #103
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But have they also been designed so that a transformer can be easily retrofitted?

Edit: It appears the electrostars can be converted to AC quite easily, as the owner wants to keep the option open to lease them to operators in AC territory.
No extra equipment is necessary, apart from the pantograph. 30 class 375/6 units and some of the class 377/2 and 377/5 already have the pantograph and already operate on overhead power supply routes such as the East Croydon - Milton Keynes services. (Actually the 375/6 rarely if ever do). And all the class 377s in service with First Capital Connect obviously use overhead power north of Farringdon.

This is not to enable the owner to have option to lease them to other areas, although this is obviously true, it is originally because the manufacturers had to allow AC retrofitting by order of the Department for Transport. It was all part of the Labour government's pledge to eradicate slam-door stock in the late 90s.

This is why not only Bombardier's Electrostars, but also Siemen's Desiros and Alstoms Junipers and are ALL retrofittable with pantographs, as they were all built under the same rules. None of them need any other electrical equipment apart from the pantograph. By design, their ability to run on DC is technically an add-on, meaning that if they were all switched to run permanently under AC, some equipment on the train would actually become redundant and could be removed. Not the other way round, where transformers needed to be added.
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Old February 12th, 2012, 02:46 PM   #104
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I mean, in the snow, the first theing the UK could do would be heating the points, but no one seems to have bothered to implement that...
Actually they are. http://www.southernrailway.com/your-...g-this-winter/ says Netwrok Rail are adding points heaters, but I couldn't find anything specific on NR's website (has anybody ever been able to find anything on their website?) but the CP4 2011 delivery programme specifies over 800 points being thus improved (but I can't find a figure specific to 3rd rail region). http://www.networkrail.co.uk/WorkAre...id=30064779395
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Old March 15th, 2012, 04:52 AM   #105
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Old June 2nd, 2012, 03:17 PM   #106
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Old June 3rd, 2012, 12:01 AM   #107
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Might there exist a passenger network of 3rd rail service where lowrise platforms exist, obliging passengers to clamber up and down the train door steps getting on or off the trains?
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Old June 3rd, 2012, 12:05 AM   #108
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Might there exist a passenger network of 3rd rail service where lowrise platforms exist, obliging passengers to clamber up and down the train door steps getting on or off the trains?
There used to be low platforms on the Metro North before 1970s...
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Old June 3rd, 2012, 12:05 AM   #109
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^I think Belmont Park LIRR station is low platform.
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Old June 4th, 2012, 06:07 PM   #110
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Might there exist a passenger network of 3rd rail service where lowrise platforms exist, obliging passengers to clamber up and down the train door steps getting on or off the trains?
Ive never really seen, it but its normal for the 3rd rail to move to the inside of the rails rather than the outside for safety, so I guess it wouldn't cause much of a problem, although I hate low rise platforms!
Glad there are none in England!
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Old September 23rd, 2012, 12:44 AM   #111
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Low-rise are dangerous. A fella passenger also waiting for a Toronto commuter train had ballast flung into his eye by a 100MPH inbound intercity. Nearly stumbling into the train whizzing by, I grabbed him while he sobbed in pain; he missed his train to go get medical help. Furthermore, brake exhaust's stinkier down at bogie level.

Anyhow, two 3rd rail systems featured between 3'00" & 5'16":
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Old September 23rd, 2012, 04:03 PM   #112
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Old September 24th, 2012, 01:46 PM   #113
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This is why not only Bombardier's Electrostars, but also Siemen's Desiros and Alstoms Junipers and are ALL retrofittable with pantographs, as they were all built under the same rules. None of them need any other electrical equipment apart from the pantograph. By design, their ability to run on DC is technically an add-on, meaning that if they were all switched to run permanently under AC, some equipment on the train would actually become redundant and could be removed. Not the other way round, where transformers needed to be added.
Are you sure about this? Isn't it the other way around? (AC is an add-on)


As far as I know modern traction systems are built like this:
  • AC: Overhead wire => Pantograph => Transformer => Rectifier => Inverter => Motor
  • DC: Overhead wire/3rd rail => Pantograph/pickup => Inverter => Motor
It can be that those trains left the factory with transformers and rectifiers for future AC use, but they are not required for DC use. The only part getting redundant after a DC/AC switch would be the 3rd-rail pickup.
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Old September 24th, 2012, 05:58 PM   #114
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Are you sure about this? Isn't it the other way around? (AC is an add-on)


As far as I know modern traction systems are built like this:
  • AC: Overhead wire => Pantograph => Transformer => Rectifier => Inverter => Motor
  • DC: Overhead wire/3rd rail => Pantograph/pickup => Inverter => Motor
It can be that those trains left the factory with transformers and rectifiers for future AC use, but they are not required for DC use. The only part getting redundant after a DC/AC switch would be the 3rd-rail pickup.
Yes I'm sure. I very much doubt those trains will have been fitted with transformers and rectifiers that aren't being used - most of these bits of equipment will have clocked up about 10 million miles over the last 10 years and generated zero revenue. In the Bombardier trains the Mitrac system is employed, and though I don't know too much it doesn't seem to be an old fashioned rectifier-inverter-DC motor configuration, but IGBT three phase traction control system feeding into AC motors. I do believe that rectifiers are no longer part of the process, but am hoping someone with loads and loads of knowledge can come inform me further.

http://www.bombardier.com/files/en/s...ITRAC_1000.pdf
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Old September 26th, 2012, 09:03 AM   #115
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Yes I'm sure. I very much doubt those trains will have been fitted with transformers and rectifiers that aren't being used - most of these bits of equipment will have clocked up about 10 million miles over the last 10 years and generated zero revenue.
Let me give you an example: The Dutch VIRM-series (built by Talbot/Bombardier) are also 'prepared for 25kV'. For this train type that means provisions have been made so a transformer and rectifier can be easily added afterward without any other major changes. Like you said, you're not going to drag around a heavy transformer for years when you do not use it, so I seriously doubt they left factory with them fitted.

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Originally Posted by makita09 View Post
I do believe that rectifiers are no longer part of the process, but am hoping someone with loads and loads of knowledge can come inform me further.
You really need rectifiers to make DC out of AC. I will try and see if I can find you some info to explain this.
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Old September 26th, 2012, 10:37 AM   #116
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You really need rectifiers to make DC out of AC. I will try and see if I can find you some info to explain this.
But many modern traction motors use AC instead. But AFAIK, you still need some kind of 'converter' because those AC motors use alternating AC (quantity of Hertz and other stuff changes over time to regulate speed and traction)
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Old September 26th, 2012, 02:27 PM   #117
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But many modern traction motors use AC instead. But AFAIK, you still need some kind of 'converter' because those AC motors use alternating AC (quantity of Hertz and other stuff changes over time to regulate speed and traction)
Take a look at this picture. This is a diagram of the traction system of a German class 152. In Germany there is 1-phase 15 kV 16,7 Hz AC on the overhead wire.

The current from the pantograph is fed into the transformer, of which the long thick line is the primary winding and the short thick bars are the secondary windings in the middle of the diagram. The secondary windings feed the rectifiers (called 4QS in Germany), feeding the Gleichspannungzwischenkreis (= DC intermediate loop). This DC loop feeds the components marked PWR which are the variable frequency drives or inverters. This are the GTO's or IGBT's you may have heard of. The VFD changes the DC into 3-phase AC, which drives the motors. The variable frequency drives can vary the voltage and frequency of the 3-phase AC to control the motors.

Thus when you have DC on your third rail or overhead wire you can feed it into the DC intermediate loop directly. The transformer and rectifier are not needed. Unfortunately I could not find a similar diagram for a class 186 or 189. They would have contained this connection.
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Old September 26th, 2012, 06:08 PM   #118
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Let me give you an example: The Dutch VIRM-series (built by Talbot/Bombardier) are also 'prepared for 25kV'. For this train type that means provisions have been made so a transformer and rectifier can be easily added afterward without any other major changes. Like you said, you're not going to drag around a heavy transformer for years when you do not use it, so I seriously doubt they left factory with them fitted.



You really need rectifiers to make DC out of AC. I will try and see if I can find you some info to explain this.
Yeah its OK I don't need a lesson on rectification

Either the rectifiers are there and are being used on both DC and AC, or they are not there and they aren't needed.

I can find no information anywhere that shows a weight difference between the AC/DC and DC units of the same class, but lots that say they are the same. The below link is one example.

http://www.therailwaycentre.com/New%...a/EMU_377.html

Bottom line is the 3rd rail trains in the UK were specified to be changed to AC operation at minimal expense. However they have done this is immaterial, but I have never heard mention of the need to do any major engineering to convert these units to AC, despite such a strategy being mentioned in the UK rail press on a regular basis owing to NR plans to change the power supply.

But the absence of further information is no reason to assume this that or the other about the situation. I keep repeating it, but its a well known fact that they can all be changed over, and within months if necessary - all of those built since the late 90s.
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Old September 27th, 2012, 08:55 AM   #119
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However they have done this is immaterial, but I have never heard mention of the need to do any major engineering to convert these units to AC, despite such a strategy being mentioned in the UK rail press on a regular basis owing to NR plans to change the power supply.
That's the good part. Nothing major is needed, just the fitting and connecting of components that were already intended to be there in the first place.

Anyway, the need for the UK to switch is bigger then most other countries using DC. At 750V it is nearly impossible to make any significant amount of power. Even a pretty standard EMU at around 1750 kW already pulls over 2300A from the 3rd rail. That also explains the big amount of large diesel locomotives in the UK. I suppose it's nearly impossible to have multiple trains in a block all using high amounts of power at the same time, say for a heavy freight train and a few EMU all trying to accellerate at the same time. In fact this same problem still occurs with 1.5kV DC on the overhead, which is why the Netherlands is also preparing for a future switch to 25kV AC.
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Old September 30th, 2012, 01:19 PM   #120
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Thats right, Network Rail is investing heavily upgrading the 750V network's power supply just to be able to operate longer trains and a handful of extra services. The main problem with 3rd rail is the need for transformers every 1 or 2 miles, which is inefficient by virtue of the increased maintenance costs, as well as the inherent limitations to the current draw. It took many years to introduce the class 375s, as their computers needed to be re-programmed to draw less current (and accelerate slower) due to the power supply.

For example, Tunbridge Wells - Hastings power supply cannot support trains longer than 8 cars, (ie one 8-car trains in each direction over any one power-block section.) Which means the commuter trains need to attach-detach to another 3/4 car unit at Tunbridge Wells.

There are all sorts of other random legacy issues too - Redhill - Tonbridge won't accept class 92 locomotives as cause signalling issues due to the 3rd rail (due to the way that stretch's signalling is isolated from the track). Waterloo - Wimbledon has a lower voltage at 630V. I can understand why NR want to go to OHLE eventually.
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