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Old January 16th, 2012, 12:40 AM   #81
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Another meddlesome advancement by the corresponding industrial sector, I bet. The only advantage I might possibly reckon would be easier, subsequent track reconfigurations to ease their excessive congestion
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Old January 25th, 2012, 06:51 AM   #82
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Old January 25th, 2012, 06:39 PM   #83
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Originally Posted by makita09 View Post
they probably will be done first, but the southern region is still a good option because it will reduce power supply costs, and the trains can mostly be retrofitted with pantographs, and those that dont they operate on certain routes, which could be done last when the units become life expired anyway.
The "cheap" electrification uses 25 kV, 50 Hz catenary. All the Southern
Region EMUs that currently use third rail power work on 750 V DC. So it's
not just a problem of merely fitting them with a pantograph, but also replacing
all DC traction systems by AC ones. When you take that into the equation,
the profitability of the operation becomes much more questionable.

Oh, and also, changing from 750V DC to 25kVAC also require to replace
all the track circuits...
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Old January 25th, 2012, 10:20 PM   #84
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Or you could just fit transformers, like on existing dual voltage EMUs.
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Old January 26th, 2012, 09:58 AM   #85
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Quote:
Originally Posted by Gag Halfrunt View Post
Or you could just fit transformers, like on existing dual voltage EMUs.
Transformers, to bring the voltage from 25 kV to 750 V and then
rectifiers to transform the AC into DC. This is usually done with
power electronics plus a large coil to obtain a reasonably stable
DC. Do you realize how big and how expensive all that stuff is ?
And you expect to install that in an EMU where no location for
it has been originally foreseen ? Is there any know case in the
world where this has already been done ?
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Old January 26th, 2012, 11:25 AM   #86
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Old January 26th, 2012, 04:20 PM   #87
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Quote:
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And you expect to install that in an EMU where no location for it has been originally foreseen ? Is there any know case in the
world where this has already been done ?
All third rail EMUs ordered since rail privatisation have recessed areas on the roof where a pantograph can be fitted. I'd assume that they also have space for transformers and rectifiers, etc.
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Old January 27th, 2012, 12:02 AM   #88
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Quote:
Originally Posted by MarcVD View Post
Transformers, to bring the voltage from 25 kV to 750 V and then
rectifiers to transform the AC into DC. This is usually done with
power electronics plus a large coil to obtain a reasonably stable
DC. Do you realize how big and how expensive all that stuff is ?
And you expect to install that in an EMU where no location for
it has been originally foreseen ? Is there any know case in the
world where this has already been done ?
You seem to forget about the existance of the Thameslink trains, running from the overhead caternary powered lines north of London, to the AC 3rd rail region in the south. They've been doing it for years. It's not exactly impossible.
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Old January 27th, 2012, 12:25 AM   #89
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Quote:
Originally Posted by MarcVD View Post
Transformers, to bring the voltage from 25 kV to 750 V and then
rectifiers to transform the AC into DC. This is usually done with
power electronics plus a large coil to obtain a reasonably stable
DC. Do you realize how big and how expensive all that stuff is ?
And you expect to install that in an EMU where no location for
it has been originally foreseen ? Is there any know case in the
world where this has already been done ?
It's not really that difficult to add the capability to draw from DC power supply, to modern AC motor controls. Thyristors basically cut, chop and paste one AC frequency to another, so converting from DC really isn't that much more difficult.
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Old January 27th, 2012, 12:27 AM   #90
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North London and West London line trains also do it. Eurostars used to do it.

However, the trains doing those runs were purpose built for that job - to convert the Southern Region to 25k Overhead, you'd need to buy a lot more of those dual-voltage trains during the transfer (though IIRC, a lot of newer DC stock in Britain has AC compatibility anyway), as - as MarcVD's point was - you can't easily convert stock that wasn't designed to carry the transformers.
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Old January 27th, 2012, 03:41 AM   #91
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Quote:
Originally Posted by Gag Halfrunt View Post
All third rail EMUs ordered since rail privatisation have recessed areas on the roof where a pantograph can be fitted
I'm curious about the contents of the memos which effectively brought about this redundancy plus who wrote them, who got 'em ... maybe veering Lucy Kellaway toward this docket might bring about another good laugh
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Old January 27th, 2012, 09:22 AM   #92
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Quote:
Originally Posted by Sopomon View Post
You seem to forget about the existance of the Thameslink trains, running from the overhead caternary powered lines north of London, to the AC 3rd rail region in the south. They've been doing it for years. It's not exactly impossible.
No, I'm not forgetting that. There are thousands of such trains on the
continent that are able to work with both DC and AC electricity supply.
But all those have been designed to do that, from the start. None were
DC only and then converted to AC afterwards. I maintain that if the space
for the transformer was not foreseen at the design stage it is not possible
to do it afterwards. Can anyone cite one case where this has been done
already ?
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Old January 27th, 2012, 10:19 AM   #93
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Quote:
Originally Posted by MarcVD View Post
The "cheap" electrification uses 25 kV, 50 Hz catenary. All the Southern
Region EMUs that currently use third rail power work on 750 V DC. So it's
not just a problem of merely fitting them with a pantograph, but also replacing
all DC traction systems by AC ones. When you take that into the equation,
the profitability of the operation becomes much more questionable.

Oh, and also, changing from 750V DC to 25kVAC also require to replace
all the track circuits...
Sorry mate, you obviously don't know that all southern region EMUs have been designed and built as AC units since the late 90s. This was a specification of the government, just in case.

Most of the southern region is operated by class 375s and class 377s - all of which can be easily retrofitted with pantographs if they don't already have them.

I do not like repeating myself.
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Old January 27th, 2012, 07:27 PM   #94
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Quote:
Originally Posted by MarcVD View Post
if the space for the transformer was not foreseen at the design stage it is not possible
Nothing prevents an operator from foresaking, e.g., seating, no?
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Old January 27th, 2012, 11:33 PM   #95
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Nothing prevents an operator from foresaking, e.g., seating, no?
Yes of course - you would probably loose something like 4 seats every
two cars. Whether the car can accomodate the additional wheight is
also another story.
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Old January 28th, 2012, 12:09 AM   #96
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Might become another excuse for folks to start slimming
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Old February 10th, 2012, 03:24 AM   #97
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,
Pros?

,
Cons?
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Old February 10th, 2012, 10:22 AM   #98
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Except that you're taking it all out of context.
3rd rail is a total mess much more often in the snow than caternary, while the cause behind the two malfunctioning pantographs are due to poor maintainence/engineering, not a flaw in the system itself brought about by external conditions.
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...
After that, then you can consider re-electrifying.
Is it any coincidence that in the Hokuriku and Tohoku regions of Japan, there are no 3rd rail powered, above ground railway systems?
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Old February 10th, 2012, 12:08 PM   #99
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Quote:
Originally Posted by makita09 View Post
Most of the southern region is operated by class 375s and class 377s - all of which can be easily retrofitted with pantographs if they don't already have them.
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.

Last edited by K_; February 10th, 2012 at 12:26 PM.
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Old February 10th, 2012, 12:11 PM   #100
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Quote:
Originally Posted by MarcVD View Post
I maintain that if the space
for the transformer was not foreseen at the design stage it is not possible
to do it afterwards.
Ofcourse it might happen that someone comes up with a Switch Mode Powersupply that doesn't require a big transformer. Doesn't exist at the moment though for rail applications.
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