MattW wrote: ↑Tue Sep 22, 2020 7:02 am
No, you misread what I wrote. I didn't say use a lower voltage in the tunnel, just a lower voltage to switch. Have a step down and step up transformer of the same ratio back to back, in between, where they're linked, you have the switchgear so you don't have to directly switch high voltage.

Doing so would lower the voltage, but at the same time you increase the current by the same ratio. For example, 12 kv to 600 volts is a 20 times reduction in voltage, there will be a 20 times increase in current. Low voltage, high current breakers have around four times the life expectancy or duty cycle, around 10,000 cycles.

So now, instead of replacing the breaker in 80 days, we are now replacing it in 320 days.

Better?

I do not believe people understand how much power is needed to run an ACS-64 locomotive.

Lets review the specifications:

Power Output

6,400 kW (8,600 hp) Maximum (Short-Time)

5,000 kW (6,700 hp) Continuous

P=IE. therefore I=P/E

I = 6,400,000 W/12,000 V = 533.333 Amps

I = 6,400.000 W/600 V = 10,666.667Amps

And that is just the power needed for just one locomotive.

Of course, that's was for the maximum rating, but that is what any breaker would have to handle for safety purposes. Locomotives decelerating probably will not need that much power - but locomotives accelerating will.