west point wrote: ↑Wed Sep 25, 2024 10:21 pm
3rd rail seems to have limitations that cannot be readily overcome.
1. MNRR limits dual mode locos to 60 MPH when running off 3rd rail. Could that be to limit current draw on the 2 pickups?? Have no idea. EMUs spread out the current draw as they have much lower max current draw.
Yup. EMUs are the answer.
2. Are engineers limited to amount of throttle on dual mode they can use in E mode? That if true would make for slower acceleration.
LIRR trains basically run at half power/acceleration, accelerating at 1.5m/s/s instead of 3m/s/s since the substations can't handle the M-7/9 cars at full power. MN limits trains north of NWP to 6 cars due to lack of power, not sure what acceleration rate they use. This is a pretty simple fix that no one wants to pay for, more and/or larger substations.
3. Is it true that present locos cannot regenerate when in E mode?
Probably. The current substations cannot invert the power back into AC to feed back to the grid. This theoretically wouldn't be hard, but to retrofit the whole system would probably cost a fortune.
4. Overhead CAT at 12.5 kV has no current draw limitations as it is the high voltage that reduce current draw.
It has current draw limitations, the current in fact is likely lower than 3rd rail, but due to the higher voltage, you still have way more power.
12. how much more weight of 25 / 60 transformers are in each piece of equipment? What is the additional ROW and track maintenance that is caused by additional weight.?
Not that much, but it's enough to make the M-8's too heavy for the Park Ave Viaduct if they had been equipped with 25hz transformers.
The 25 NEC may have been one factor of CA HSR and Amtrak going separate ways for rolling stock.
There's a MUCH larger issue with bespoke equipment than 25hz. The larger transformer probably has a negligible impact on design, and agencies that don't need it could just order the same car with a smaller transformer for 60hz only.
I'm not convinced that converting from 25hz to 60hz has that big of an impact on anything. I think the capital cost would be much better spent on about 100 other projects. The 25hz railroads also have ACSES II instead of I-ETMS, and while virtually every railroad in the rest of the country is cleared to at a bare minimum 16'2", many of the 25hz railroads are 15'6" or less. So the NEC stuff is all sort of bespoke anyway, and adding 25hz transformers to it is a relatively negligible cost in the whole scheme of things.
Jeff Smith wrote: ↑Fri Sep 27, 2024 7:52 amBenefit: you'd be able to have a single-MU fleet that could run anywhere with a single-type shoe.
The M-8 fleet has double-sided shoes and will be using both types of 3rd rail, potentially in the same day when PSA opens, so it's sort of a nothingburger.
west point wrote: ↑Sat Oct 05, 2024 11:12 pm
1. MBTA is going to install 60 hZ CAT sooner or later. Their units will not be able to enter the PRR type 25 hZ,
Depends if they have 25hz transformers or not.
However, there are some that cannot change on the fly from the NJT 25 kV power to 12 kV.
Old EMUs. All the newer stuff like the ALP's can convert on the fly.
4. The MN RR EMUs that use CAT are all 60 hZ only. It has been reported that a 25 / 60 hZ transformer is too heavy in them to operate on the Park Ave viaduct. No indication if the viaduct rehab will remove that restriction.
That was correct. With the revised FRA crash standards, I would suspect that a clean-sheet M-10 design could probably have a 25hz transformer due to not needing to be quite so absurdly overbuilt like the M-8 cars that meet the old crash standards that are based on running into a coal train at track speed (or something like that).