Amtrak Empire, LIRR, MNRR/CTDOT Dual Mode Procurement - Charger Variants

STrRedWolf wrote: ↑Fri Jul 10, 2020 4:33 pm Well... what's heavier? Diesel + third rail, or diesel + catenary?

Latter. Take a look at the ALP45. Bulky and not high on fuel economy.

Early 1990's LIRR put together a train from some Japanese double decker cars and 2 of 3 on hand rebuilt and modernized FL9AC's. Ignoring how LIRR used one of the 3 as a parts source (meaning there were no spare locos if one of them died - which was frequent), there were some regular problems with the locos. At the top of the list were the inverters. Now I know it was 3rd rail, not cat, and I believe that while the 3rd rail power was DC, it had AC traction, hence the inverters. They frequently burnt out, supposedly because of inadequate ventilation. Metro North (using a variation of the same FL9AC's) would, once in a while, dole out a replacement inverter (they were very expensive). End result is that for many reasons, the 'BITANIC' was frequently out of service while awaiting parts. And with no backup loco, no way to deal with the problems. There were other issues. Dead storage batteries in the cars. Magnetic between car cable connections which didn't work well (eventually they were replaced by standardized connectors between cars. The locos where heavily computerized - described as bleeding edge.

IOTW, any way to avoid inverters sounds good.

Virtually everything is inverter driven these days , one way or the other. Even diesel locomtives. I'd say the problem is in the small batch and trying to mix and match , Once set up right they are very reliable.

R36 Combine Coach wrote: ↑Fri Jul 10, 2020 4:51 pm

STrRedWolf wrote: ↑Fri Jul 10, 2020 4:33 pm Well... what's heavier? Diesel + third rail, or diesel + catenary?

Latter. Take a look at the ALP45. Bulky and not high on fuel economy.

If you aren’t concerned with having a high-powered AC unit and mid-powered diesel like the ALP-45DP, but are content with the same or less power from the AC half, I bet you could make a much lighter dual-mode diesel/cat locomotive. Maybe the AC part would be light & compact enough to use the same prime mover with a half-size fuel tank.

David Benton wrote:Virtually everything is inverter driven these days , one way or the other. Even diesel locomtives. I'd say the problem is in the small batch and trying to mix and match , Once set up right they are very reliable.

Exactly. The FL9AC was the problem (the follow-on DM30AC isn’t great either), while the inverter-equipped GE P32ACDM has been pretty reliable until heavy use & age began taking its toll.

David is correct, plus you have thirty years of inverter development to count on. We use inverters in cranes every day and the difference from 1990 and 2020 is leaps and bounds. What was once the size of a refrigerator can now be the size of a shoebox.

Tadman wrote: ↑Fri Jul 10, 2020 8:02 pm David is correct, plus you have thirty years of inverter development to count on. We use inverters in cranes every day and the difference from 1990 and 2020 is leaps and bounds. What was once the size of a refrigerator can now be the size of a shoebox.

If you're doing Diesel AC, AC Catenary (NEC), and AC motive bogies, it makes sense to keep it all AC as much as possible. The whole system is kept simple. The only issue you'd have is the need for a frequency converter if the system is 60 Hz AC and you're pulling 25 Hz power. But if anything's DC, you'll need a rectifier and inverter.

That said, I bet that shoebox will shrink further. I don't know if the latest tech using gallium nitride (GaN) is what gets it down to shoebox size, or if it will let it go even smaller.

It doesn’t work quite like that, as far as I know anyway. I think the current standard is to take the high-voltage single-phase AC from either the traction alternator or catenary, rectify it into very-high-voltage DC, then invert & chop it into multi-phase AC which powers the motors (and is throttled via frequency modulation.) That is, the supply frequency and not the voltage or amperage dictates the motor speed - if the system is 60 Hz, the motor would only run at 3600 rpm (or would stall if not supplied with enough voltage or amperage.) Same with 25 Hz, the motor would only rotate at 1500 rpm.

I don’t know of a way to directly convert single-phase fixed-frequency AC to multi-phase variable-frequency AC without an intermediate DC step.

mtuandrew wrote: ↑Fri Jul 10, 2020 10:43 pm It doesn’t work quite like that, as far as I know anyway. I think the current standard is to take the high-voltage single-phase AC from either the traction alternator or catenary, rectify it into very-high-voltage DC, then invert & chop it into multi-phase AC which powers the motors (and is throttled via frequency modulation.) That is, the supply frequency and not the voltage or amperage dictates the motor speed - if the system is 60 Hz, the motor would only run at 3600 rpm (or would stall if not supplied with enough voltage or amperage.) Same with 25 Hz, the motor would only rotate at 1500 rpm.

I don’t know of a way to directly convert single-phase fixed-frequency AC to multi-phase variable-frequency AC without an intermediate DC step.

Wow, I was in the process of making a post about this exact thing! You beat me to it by three minutes.

Yes, there is no such thing as "keeping it all AC". This thread has some description of the intermediate DC link as implemented in the ACS-64. http://cs.trains.com/trn/f/743/t/217694.aspx

Also, as far as the FL9AC, don't forget that they used very early GTO thyristor based inverters, which were far less reliable than modern IGBT transistor based inverters. Only a select few thyristor AC traction passenger locomotives ended up being at all successful in the U.S., mainly the P32ACDM and original ALP-46 order.

Amtrak706 wrote: ↑Fri Jul 10, 2020 10:52 pmWow, I was in the process of making a post about this exact thing! You beat me to it by three minutes.

Yes, there is no such thing as "keeping it all AC". This thread has some description of the intermediate DC link as implemented in the ACS-64. http://cs.trains.com/trn/f/743/t/217694.aspx

Also, as far as the FL9AC, don't forget that they used very early GTO thyristor based inverters, which were far less reliable than modern IGBT transistor based inverters. Only a select few thyristor AC traction passenger locomotives ended up being at all successful in the U.S., mainly the P32ACDM and original ALP-46 order.

Thanks for confirming I got it right!

Is the AEM-7AC thyristor-based too?

mtuandrew wrote:

Amtrak706 wrote: ↑Fri Jul 10, 2020 10:52 pmWow, I was in the process of making a post about this exact thing! You beat me to it by three minutes.

Yes, there is no such thing as "keeping it all AC". This thread has some description of the intermediate DC link as implemented in the ACS-64. http://cs.trains.com/trn/f/743/t/217694.aspx

Also, as far as the FL9AC, don't forget that they used very early GTO thyristor based inverters, which were far less reliable than modern IGBT transistor based inverters. Only a select few thyristor AC traction passenger locomotives ended up being at all successful in the U.S., mainly the P32ACDM and original ALP-46 order.

Thanks for confirming I got it right!

Is the AEM-7AC thyristor-based too?

Nope, it is IGBT. I've been told it was actually the first locomotive with IGBT inverters for traction in the world.

Amtrak706 wrote: ↑Fri Jul 10, 2020 10:52 pm

mtuandrew wrote: ↑Fri Jul 10, 2020 10:43 pm It doesn’t work quite like that, as far as I know anyway. I think the current standard is to take the high-voltage single-phase AC from either the traction alternator or catenary, rectify it into very-high-voltage DC, then invert & chop it into multi-phase AC which powers the motors (and is throttled via frequency modulation.) That is, the supply frequency and not the voltage or amperage dictates the motor speed - if the system is 60 Hz, the motor would only run at 3600 rpm (or would stall if not supplied with enough voltage or amperage.) Same with 25 Hz, the motor would only rotate at 1500 rpm.

I don’t know of a way to directly convert single-phase fixed-frequency AC to multi-phase variable-frequency AC without an intermediate DC step.

Wow, I was in the process of making a post about this exact thing! You beat me to it by three minutes.

Yes, there is no such thing as "keeping it all AC". This thread has some description of the intermediate DC link as implemented in the ACS-64. http://cs.trains.com/trn/f/743/t/217694.aspx

Also, as far as the FL9AC, don't forget that they used very early GTO thyristor based inverters, which were far less reliable than modern IGBT transistor based inverters. Only a select few thyristor AC traction passenger locomotives ended up being at all successful in the U.S., mainly the P32ACDM and original ALP-46 order.

This is all correct. To oversimplify, you can't just feed AC out of the catenary into the traction motors, you have to control it (to control speed and pulling). With industrial voltage, you can't just feed it through a switch or rheostat like they once did. (this was a thing - early streetcars and cranes had the line voltage go right through the operator control - DANGEROUS!!)

The inverters take the line AC, translate it to the different AC that the motors require, and meter it out to control the motor power and vehicle speed.

Weren't the ALP45-DPs created for the concept of using the pans as the primary source and the diesel for last mile? If true, that would mean fuel efficiency was secondary, almost immaterial. Yes, I understand "last mile" here is a bit of a misnomer particularly on the Raritan Valley line or for future service on West of Hudson lines if a loop was ever built. However, whether on those lines or on the NJCL where there is more electric mileage than diesel the point is that electric power needed to be either the primary focus or equal to diesel power. Amtrak, MetroNorth, and LIRR only need electric for true "last mile" service and, therefore, much lower power requirements and, presumably, weight.

Could a pan-equipped motor make sense for Amtrak and LIRR? It would need enough power for a slow slog through the tunnels and for HEP, not for any type of high speed acceleration (other than to clear out of the station in a timely fashion and not become a bottle neck). What are the speed limits within the electric only zones of Penn and Sunnyside?

Metro North would be much more difficult because of different clearance issues and lack of AC catenary to begin with. Since that would make a single spec joint purchase impossible perhaps it is either (A) not worth it at all or, (B) more worth it to examine routing all MN diesel trains via West Side or Hell Gate to Penn and require a transfer somewhere for NYG.

Any thoughts on the other bids put in?

andegold wrote: ↑Sat Jul 11, 2020 9:48 am Weren't the ALP45-DPs created for the concept of using the pans as the primary source and the diesel for last mile? If true, that would mean fuel efficiency was secondary, almost immaterial. Yes, I understand "last mile" here is a bit of a misnomer particularly on the Raritan Valley line or for future service on West of Hudson lines if a loop was ever built. However, whether on those lines or on the NJCL where there is more electric mileage than diesel the point is that electric power needed to be either the primary focus or equal to diesel power. Amtrak, MetroNorth, and LIRR only need electric for true "last mile" service and, therefore, much lower power requirements and, presumably, weight.

Could a pan-equipped motor make sense for Amtrak and LIRR? It would need enough power for a slow slog through the tunnels and for HEP, not for any type of high speed acceleration (other than to clear out of the station in a timely fashion and not become a bottle neck). What are the speed limits within the electric only zones of Penn and Sunnyside?

Metro North would be much more difficult because of different clearance issues and lack of AC catenary to begin with. Since that would make a single spec joint purchase impossible perhaps it is either (A) not worth it at all or, (B) more worth it to examine routing all MN diesel trains via West Side or Hell Gate to Penn and require a transfer somewhere for NYG.

The ALP-45DP was designed as an equal parts diesel and AC electric. Neither mode was intended to be last-mile. NJ Transit uses them on diesel-exclusive trains as well as electric-exclusive trains, and they perform decently well on both. This is why they are so heavy - they have full AC gear as well as dual CAT diesels for 4200hp. They are allowed 90mph in either mode, unlike the P32ACDM which is allowed only 60mph in DC electric mode, down from 110mph in diesel. I believe the DM30AC is good for 80 in DC electric mode but it may also be restricted to 60. Similarly, the ALP-45DP is designed for 125 in electric mode and 100 in diesel mode, but has been restricted to 90 by Amtrak as a side effect of their weight.

Ruling grade for the dual mode diesels is under the East River. This is also where they reach their highest speed in electric mode, as track speed in the tunnels is 60mph. Performance criteria for a DC dual mode should be derived from this area.

I would say the current method of DC third rail for last mile and diesel otherwise works fine. No need to reinvent the wheel where it doesn't need to be reinvented, especially if you are introducing new issues like maintaining two units or dragging around a lot more dead weight. There isn't really anywhere that a dual cab design would save any time, as Amtrak trains have to run around the loop at Sunnyside to reach the yard and LIRR/MN trains are push-pull.