[GTALUG] mysterious restarts

[Lennart Sorensen]

On Wed, Jun 15, 2016 at 11:01:44AM -0400, Russell Reiter via talk wrote:
> Take a look at a trolly pole then a pantograph array and tell me the
> pantograph needs less maintainence till EOL. You've never heard of a
> trolly pole monitoring station, there is a pantograph monitoring
> station though. It's higher voltage capacity that is the reason this
> form factor takes dominance in overhead wiring.

Less maintainance for the power lines, not for the pickup part on the
train.  The intersection switches needed for trolleypole are complex
compared to the trivial wire used with the pantograph.  I would be
surprised if the train part of the system isn't a bit more complex to
maintain with the pantograph.

Of course another advantage is that a pantograph doesn't fall off
the wire.

> As you said higher vehicle speeds are a moot point in Toronto.

Completely.

> So doesn't economy of scale account for the sensibility of starting
> with a higher DC voltage when part of the load is inverted back to AC
> for motors? I'm assuming the onboard solid state keeps the input at
> DC, rectifying it again would go beyond the pale.

Well the pantographs needed the larger diameter wire to get a larger
contact surface anyhow.  Trolleypoles seem much better at making contact
around a wire, than the flat contact of the pantograph, well until they
fall off.

The electicity usage stays pretty much the same no matter what voltage
you use, although you have some voltage loss over wire distance, which
does give higher voltage a slight benefit, but 750 versus 600 is hardly
enough to really matter.  It all just comes down to voltage * current
in the end.  Incraease voltage and you decrease current and get the
same result.  Maybe the invertor is more efficient with some input
voltages than others, but again, it isn't a big voltage difference so
probably doesn't matter much.

-- 
Len Sorensen