Why do the trains on the NLL switch over to 25Kv AC at Hackney Wick
and then switch back to DC at Dalston when the 3rd rail is continuous
along that section anyway? Why not just stay on DC and save the wear
and tear on the pantograph?

B2003

Boltar wrote:
Why do the trains on the NLL switch over to 25Kv AC at Hackney Wick
and then switch back to DC at Dalston when the 3rd rail is continuous
along that section anyway? Why not just stay on DC and save the wear
and tear on the pantograph?


Mainly because the Class 313s work better on AC than on DC. They were
originally designed as an AC unit with the DC only for the short
section from Drayton Park - Moorgate and reliability suffered when
they first transferred to the North London Line. Of course, from next
year when the new platforms open at Stratford, they will run on AC all
the way from Stratford to Dalston.

"Andy" wrote in message
...
Boltar wrote:
Why do the trains on the NLL switch over to 25Kv AC at Hackney Wick
and then switch back to DC at Dalston when the 3rd rail is continuous
along that section anyway? Why not just stay on DC and save the wear
and tear on the pantograph?


Mainly because the Class 313s work better on AC than on DC. They were
originally designed as an AC unit with the DC only for the short
section from Drayton Park - Moorgate and reliability suffered when
they first transferred to the North London Line. Of course, from next
year when the new platforms open at Stratford, they will run on AC all
the way from Stratford to Dalston.

and when ELLX gets to Highbury & Islington the NLL tracks will be AC between
Dalston and Camden Road, and the new NLL trains will run on AC all the way
from Stratford to Acton.

Peter

On 17 Jan, 16:31, "Peter Masson" wrote:
"Andy" wrote in message

...

Boltar wrote:
Why do the trains on the NLL switch over to 25Kv AC at Hackney Wick
and then switch back to DC at Dalston when the 3rd rail is continuous
along that section anyway? Why not just stay on DC and save the wear
and tear on the pantograph?

Mainly because the Class 313s work better on AC than on DC. They were
originally designed as an AC unit with the DC only for the short
section from Drayton Park - Moorgate and reliability suffered when
they first transferred to the North London Line. Of course, from next
year when the new platforms open at Stratford, they will run on AC all
the way from Stratford to Dalston.

and when ELLX gets to Highbury & Islington the NLL tracks will be AC between
Dalston and Camden Road, and the new NLL trains will run on AC all the way
from Stratford to Acton.

Will the 3rd rail be lifted then?

B2003

"Boltar" wrote

and when ELLX gets to Highbury & Islington the NLL tracks will be AC
between
Dalston and Camden Road, and the new NLL trains will run on AC all the
way
from Stratford to Acton.

Will the 3rd rail be lifted then?

The whole lot will probably have to be relaid anyway, to provide 4 platforms
at Canonbury and Highbury, and 4 tracks on the current 3-track section. I
can't see the juice rail surviving all that (except on the ELLX lines
between Dalston Junction and Highbury & Islington, as the ELLX will be an
entirely DC operation, and its trains, though in other respects essentially
the same as the new trains for the NLL, will be DC only).

Peter

On 17 Jan, 16:44, "Peter Masson" wrote:
"Boltar" wrote

and when ELLX gets to Highbury & Islington the NLL tracks will be AC
between
Dalston and Camden Road, and the new NLL trains will run on AC all the
way
from Stratford to Acton.

Will the 3rd rail be lifted then?

The whole lot will probably have to be relaid anyway, to provide 4 platforms
at Canonbury and Highbury, and 4 tracks on the current 3-track section. I
can't see the juice rail surviving all that (except on the ELLX lines
between Dalston Junction and Highbury & Islington, as the ELLX will be an
entirely DC operation, and its trains, though in other respects essentially
the same as the new trains for the NLL, will be DC only).

Peter

Obviously under the arrangement for the ELLX up to Highbury &
Islington that has become apparent lately there's no need for the ELLX
rolling stock to have AC equipment, but I was under the impression
that all the new class 378 Electrostar trains for London Overground
were all ordered as dual system (i.e. AC & DC) stock - am I wrong in
thinking this, or has the order subsequently been amended?

"Mizter T" wrote

Obviously under the arrangement for the ELLX up to Highbury &
Islington that has become apparent lately there's no need for the ELLX
rolling stock to have AC equipment, but I was under the impression
that all the new class 378 Electrostar trains for London Overground
were all ordered as dual system (i.e. AC & DC) stock - am I wrong in
thinking this, or has the order subsequently been amended?

November 2007 MR stated 'TfL has ordered 20x4-car Electrostars for the ELL
(plus 108 vehicles for the NLL and Euston - Watford DC). The ELL units will
be DC trains, although they will have provision for AC to be provided at a
later date if necessary".

Peter

On Jan 17, 5:15*pm, Mizter T wrote:
On 17 Jan, 16:44, "Peter Masson" wrote:



"Boltar" wrote

and when ELLX gets to Highbury & Islington the NLL tracks will be AC
between
Dalston and Camden Road, and the new NLL trains will *run on AC all the
way
from Stratford to Acton.

Will the 3rd rail be lifted then?

The whole lot will probably have to be relaid anyway, to provide 4 platforms
at Canonbury and Highbury, and 4 tracks on the current 3-track section. I
can't see the juice rail surviving all that (except on the ELLX lines
between Dalston Junction and Highbury & Islington, as the ELLX will be an
entirely DC operation, and its trains, though in other respects essentially
the same as the new trains for the NLL, will be DC only).

Peter

Obviously under the arrangement for the ELLX up to Highbury &
Islington that has become apparent lately there's no need for the ELLX
rolling stock to have AC equipment, but I was under the impression
that all the new class 378 Electrostar trains for London Overground
were all ordered as dual system (i.e. AC & DC) stock - am I wrong in
thinking this, or has the order subsequently been amended?

The class 378 units will be split into two. The replacements for the
class 313 will be dual voltage. The 'extras' for the ELLX will be DC
only, at least initially, but will have passive provision for AC as
well. I wouldn't be surprised if all the units end up as dual voltage,
especially as the services for Phase 2 of the ELLX might change
depending on loadings after phase 1 is completed.

On 17 Jan, 17:15, Mizter T wrote:
Obviously under the arrangement for the ELLX up to Highbury &
Islington that has become apparent lately there's no need for the ELLX
rolling stock to have AC equipment, but I was under the impression
that all the new class 378 Electrostar trains for London Overground
were all ordered as dual system (i.e. AC & DC) stock - am I wrong in
thinking this, or has the order subsequently been amended?

You're wrong, I think: TfL's original press release mentions that the
NLL ones would be dual-voltage (and hence implies that the ELL ones
wouldn't be):
http://www.tfl.gov.uk/corporate/medi...ntre/3534.aspx

Of course, the ELL ones will have pantograph spaces and will be
electronically capable of AC/DC operation, like all new 3rd rail
stock.

--
John Band
john at johnband dot org
www.johnband.org

On Jan 17, 9:42 am, John B wrote:


Of course, the ELL ones will have pantograph spaces and will be
electronically capable of AC/DC operation, like all new 3rd rail
stock.


Indeed, this is a key point for all present generation EMU.

Although in the general case of all types (i.e. beyond the 378s being
discussed above) it might be more than just a pantograph tp be added -
some existing classes would need - or might need in future if ordered
without - a transformer to be needed as well.

But yes power electronics are already capable.

--
Nick