[GTALUG] mysterious restarts

[Bob Jonkman]

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Russell writes:
> Take a look at a trolly pole then a pantograph array and tell me
> the pantograph needs less maintainence till EOL

It's not the pantograph that requires less maintenance, it's the
overhead wires. A single trolley pole requires the overhead wire to
have switches (like track switches, not electrical switches) at
intersections and any location where the streetcar can choose a
direction. Very often there are disconnections as the trolley pole
moves from one wire to another. That can't be good for the circuitry.
And how often does the trolley pole come disconnected from the
overhead wire?

OTOH, the wires for the pantograph can be continuous, there can be
multiple wires at intersections, and there are far fewer
disconnections, intentional or accidental.

- --Bob.


On 2016-06-15 11:01 AM, Russell Reiter via talk wrote:
> 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
>> 
> --- Talk Mailing List talk at gtalug.org 
> https://gtalug.org/mailman/listinfo/talk
> 
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