BandA wrote:MBTA blue line subway cars have or had catenary + 3rd railVery different systems you're talking here.
How big is a transformer for these electric locomotives, and how much do they weigh? I can't wrap my head around why electric locos aren't much smaller than diesel-electric which has to carry a big diesel + generator
Blue Line is the same exact 600V DC power source whether it comes from the 3rd rail or pantograph. Actually, Blue Line is same exact 600V DC power source as Red, Orange, Green, the Mattapan trolley, the Silver Line dual-mode buses, and the Cambridge trackless trolleys. It takes zero additional electrical equipment to run on any MBTA traction power other than wiring to the roof for a pantograph mount vs. wiring to the underside for 3rd rail shoe mounts. It's why the Orange Line 01200 cars came out of the same factory with the same pantograph mounting plugs on the roof as the Blue Line 0600's. Seashore Trolley Museum runs all of its ex-MBTA heavy rail cars on its trolley overhead simply by attaching a trailer to the cars with a trolley pole and jumper cables connected to the 3rd rail shoes on the car. Same voltage any which way...the difference is only in the means of physical contact: pantograph, trolley pole, or shoes.
On the RR you have 750V DC 3rd rail on Metro North and LIRR...fully electrically compatible if you have the flippable shoes like the M8's that can do under-running MNRR 3rd rail or over-running LIRR 3rd rail. But then you've got the AC overhead on the NEC. 60 Hz/12.5 kV is a transformer core completely different from the DC inputs, and it takes a lot of additional equipment to switch on-the-fly between such different power sources. That's more weight on an M8. 60 Hz/25 kV for Shore Line East running is yet another heavy transformer core on top of the 12.5 kV one. Now you've got 3 power inputs in one vehicle and pretty close to the heaviest EMU in active service. Kawasaki offered a purchase option to configure the M8's for 25 Hz/12.5 kV...but the 25 Hz transformer cores are the heaviest of them all and would've left the cars so seriously overweight they'd likely have had all sorts of other design and mechanical problems to contend with related to the excess bulk. As is, the DC + AC inputs require so many extra components on the underside of the cars that it's going to be physically impossible--at least for the next few decades--to ever design a New Haven Line EMU in MLV dimensions. They're stuck with single-levels pretty much forever, unlike NJT which is ordering its Arrow-replacement EMU's in the MultiLevel coach carbody.
It's somewhat easier to have just the AC-only cores. Every electric locomotive sold here comes out-of-the-box equipped for 25 Hz/12.5 kV, 60 Hz/12.5 kV, and 60 Hz/25 kV. As do the Silverliner V EMU's and these next-gen NJT EMU's. As do the ALP-45DP diesel dual-modes. They're all heavier than they could/should be because the NEC electrification is so fragmented. It would be a lot easier for everyone if 25 Hz got phased out and everyone could consolidate on just the two 60 Hz voltages for significant weight savings, but Amtrak made its bed with refurbing the 25 Hz infrastructure so we're stuck with it. Other fresh electrifications elsewhere in the U.S. and Canada that start from Day 1 at 60 Hz/25 kV have the advantage of being able to buy equipment with only one transformer core at all the cost and weight savings that brings. The Euros have so much continental standardization on 25 kV AC that they have it a little easier only needing to do one AC core, one [other] core, and segmenting their equipment pools. They likewise can't possibly unite every mainline electrification scheme on the continent in one vehicle only without being impractically heavy, but unlike the three-headed voltage monster on the NEC there are few routes that have a need for changing between >2 electrification schemes on the same trip. The trains that do are outliers few enough in number that an engine switch somewhere en route usually does the trick with greater efficiency than larding up the rolling stock to absurdity. It's unavoidable here because of the NEC's voltage fragmentation.
So unfortunately, all four electrification schemes under one hood is just a bridge too far. Even the spacious environs of a locomotive carbody is going to have trouble fitting the DC equipment inside and staying within weight when it has no choice but to carry at least 2-3 other AC voltage cores to adequately roam anywhere on the NEC. To do that you pretty much do have to consolidate from 3 to 2 AC cores to create the room and shed enough weight to re-load. Which means spending the $B's to convert at least one of the NEC power sources--probably the 25 Hz--to another. And even then, the possible routes where it would be worth it to consolidate power just don't exist. Amtrak can't run thru from the NEC to the Empire because the tunnels point the wrong way, and there's the diesel gap on the Empire Connection so the Metro North 3rd rail isn't a factor anyway. LIRR splits from the NEC out in open air and LIRR 3rd rail runs to the North River portal on the NJ side, so you only need one either/or type of diesel dual-mode--not both--to get from any side of Penn to any other side of Penn and anywhere on Long Island. It can be done today with a P32 or ALP45-DP, so the only thing lost vs. your hypothetical 4-input all-electric is needing to do some diesel running and picking which vehicle spends more time in E-mode: a 3rd rail dual that runs diesel from New Jersey-south or a pantograph dual that runs on diesel from Sunnyside-east onto Long Island. GCT does have the diesel layup tracks if the schedule is small enough for that limited platform space to be adequate, so you can bring an ALP-45DP in there too for special-event trains points east to Boston. And if NYSHSR electrification ever happens to Albany then the Empire Connection and Hudson Line 3rd rail past Spuytien Duyvil is going to get replaced with 60 Hz/25 kV AC overhead and Metro North is going to start running New Haven Line EMU's on the entire Hudson schedule, changing from under-running 3rd rail to 25 kV overhead at SD on GCT runs and LIRR over-running 3rd rail to 25 kV overhead on the Empire Connection to avoid the short length of 25 Hz overhead in the tunnel that they can't run on.
So not even in the future is there going to be a single route scenario that pops up where you have to unite every electrification scheme under the hood of one vehicle. The diesel dual-modes obviate that need now and forever, with Penn's overhead + 3rd rail portal-to-portal configuration making the changeovers straightforward today if you had the vehicles and ridership demand in sufficient numbers to launch such a service.
