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


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