[GTALUG] mysterious restarts

Russell Reiter rreiter91 at gmail.com
Wed Jun 15 11:01:44 EDT 2016


On 6/15/16, Lennart Sorensen <lsorense at csclub.uwaterloo.ca> wrote:
> On Tue, Jun 14, 2016 at 05:57:44PM -0400, Russell Reiter wrote:
>> I don't doubt it at all. I don't understand not taking advantage of the
>> pantographic ability to carry higher voltage; that is its primary
>> feature.
>
> Actually the primary feature is less maintenance, simpler wiring, and
> higher speed supported (not that you need that in Toronto streets).

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.

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

>
>> That would be like buying a Porsche and detuning the turbo, just doesn't
>> follow common sense.
>
> Well all that really matters is how much power they can deliver, so
> voltage * current.  Higher voltage means less current, but also bigger
> insulators needed.  It's a tradeoff.  Given they already have 600V
> equipment, sticking with that makes sense.  After all increasing the
> insulator length might not be practical based on the height of the
> mounting point for the current wires.
>
>> On the other hand, for future capacity planning while load balancing the
>> polyphase AC grid we draw that energy from, the advantage of inverting to
>> higher DC voltage under higher demand, does make sense.
>
> Well I am quite sure they are running AC motors, so they would be taking
> the DC and inverting it to AC and making it whatever voltage they need
> at the time for the motors.

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.

>
> --
> Len Sorensen
>


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