On 17 Jan, 19:07, D7666 wrote:
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

ELL units will be DC only and all others will be AC/DC..
Dazz285

On Thu, 17 Jan 2008, D7666 wrote:

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.

And a rectifier, i assume. Or do modern DC trains work by inverting the DC
into a low-voltage AC at the same frequency as an OHLE supply and using
that to work a motor?

You say 'some' - does that mean there are trains which have a transformer
but no pantograph? It makes sense to build a system to which the AC bits
could be added later, and to leave room for a transformer etc, but
installing a transformer which will just sit there being dead weight seems
a bit crazy.

Do DEMUs get built so they can be upgraded to OHLE (or third rail!)
operation too?

tom


--
Gotta have skills to pay those bills.

On Jan 17, 7:55*pm, Tom Anderson wrote:
On Thu, 17 Jan 2008, D7666 wrote:
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.

And a rectifier, i assume. Or do modern DC trains work by inverting the DC
into a low-voltage AC at the same frequency as an OHLE supply and using
that to work a motor?

You say 'some' - does that mean there are trains which have a transformer
but no pantograph? It makes sense to build a system to which the AC bits
could be added later, and to leave room for a transformer etc, but
installing a transformer which will just sit there being dead weight seems
a bit crazy.

There is often a loud buzzing in the coach on a 376 which has the
space for the pantograph. I don't know if this implies the relevant
equipment.


Do DEMUs get built so they can be upgraded to OHLE (or third rail!)
operation too?

There aren't any DEMUs are there, apart from Voyagers?

On Jan 17, 7:55*pm, Tom Anderson wrote:
On Thu, 17 Jan 2008, D7666 wrote:
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.

And a rectifier, i assume. Or do modern DC trains work by inverting the DC
into a low-voltage AC at the same frequency as an OHLE supply and using
that to work a motor?


Modern EMUs use three phase traction motors and both AC and DC line
voltages need to be converted for the three phase power electronics.

You say 'some' - does that mean there are trains which have a transformer
but no pantograph? It makes sense to build a system to which the AC bits
could be added later, and to leave room for a transformer etc, but
installing a transformer which will just sit there being dead weight seems
a bit crazy.


The class 375/6 are dual voltage units, delivered complete with
pantographs, but have never used the AC equipment in anger (except
maybe for some tests, I don't know) and several have had the
pantographs removed.
I think that quite a few of the other 375 and 377 subclasses also at
least the transformer fitted, the heaviest coaches in the units are
the driving coaches and an extra tonne or four in the trailers won't
make much difference to performance!! All the four car units have
three motor coaches and so outperform the units that they replace, I
don't think that weight was an important part of the design process.
Captain Deltic's description for the new generation of units is 'power
hungry lardbutts'

On 17 Jan, 20:32, Andy wrote:
Modern EMUs use three phase traction motors and both AC and DC line
voltages need to be converted for the three phase power electronics.

My understanding is that when you have three-phase AC motors, all
power sources (AC, DC and diesel) are converted to DC at some point,
before being fed into the electronics that create the three-phase for
the motors. So in theory they should all be interchangeable, but I
doubt it's that simple.

U

--
http://londonconnections.blogspot.com/
A blog about transport projects in London

"Tom Anderson" wrote in message
.li...
On Thu, 17 Jan 2008, D7666 wrote:

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.

And a rectifier, i assume. Or do modern DC trains work by inverting the DC
into a low-voltage AC at the same frequency as an OHLE supply and using
that to work a motor?

You say 'some' - does that mean there are trains which have a transformer
but no pantograph? It makes sense to build a system to which the AC bits
could be added later, and to leave room for a transformer etc, but
installing a transformer which will just sit there being dead weight seems
a bit crazy.

That certainly seems to be the case with the Desiros, the WCML 350s (which
are basically the same train as the SWT 450s), have a PTSO 10t heavier than
the DC versions TSO, according to the Platform 5 book.

Paul

On Jan 17, 1:32 pm, "Paul Scott"
wrote:

have a PTSO 10t heavier than
the DC versions TSO,


;o)

TSO and PTSO really ought to give you a clue before looking at the
weights !

;o)

--
Nick

On 17 Jan, 21:39, D7666 wrote:
have a PTSO 10t heavier than
the DC versions TSO,

;o)

TSO and PTSO really ought to give you a clue before looking at the
weights !

;o)

OTOH, 10 tonnes seems a bit heavy-duty for a pantograph. Is it an SNCF
design...?

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

Speaking of ELLX, has TfL put up any Webcams anywhere along the route under
construction to watch their progress?

Sorry if slightly off-topic.

"D7666" wrote in message
...
On Jan 17, 1:32 pm, "Paul Scott"
wrote:

have a PTSO 10t heavier than
the DC versions TSO,


;o)

TSO and PTSO really ought to give you a clue before looking at the
weights !

;o)


What I was pointing out was that 10t is more than just the pantograph
weight?

Paul