In article
,
andypurk@gmail.com (Andy) wrote:

> On Sep 17, 4:34 pm, rosenst...@cix.co.uk (Colin Rosenstiel) wrote:
> > In article
> ,
> > ch...@kuching.co.uk (somersetchris) wrote:

> > > The reason why the trains switch to AC is because trains using the 
> > > DC stretch along there would have to go at half power.
> >
> > Isn't that just a general feature of the 313s? As built for the GN 
> > they ran in series only on DC because the Northern City Line section
> > is limited to 30 MPH anyway. It doesn't affect the 508s and I thought

> > the 313s transferred to the NLL/Euston Watford Service were modified.
> 
> Yes, I think this is the case. The Northern City trains are limited to
> 30 mph in the tunnels anyway. I don't think that there is any
> difference in the power available under DC or AC. If there was any DC
> speed limiters on the original units, they have certainly been removed
> from the NLL units.

I don't think there was anything to "remove". The DC controls were
series-only. They would have had to be modified for full series-parallel
control, something not quite so simple.

-- 
Colin Rosenstiel