On 6/15/16, Lennart Sorensen <lsorense@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