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?