Is it possible to create a locomotive that runs on diesel, third rail, and overhead wires?

[shredder]

Yes. British railways Class 74 existed in mid-1960s. The similat, but without overhead capability, Class 73 still exists.

[erikem]

Wizlish

 It is quite possible to build a switch-mode dc-dc converter with power FETs and SiC Schottky diodes that will handle high voltage, and run it at as high frequency as your electronic noise tolerance allows.  Note that this does not involve inductive coupling as in a transformer, and does not involve "AC" conversion in the normal sense.  In my opinion, if you wanted to take third-rail power (at 600 to 750 VDC) and transvert it for compatibility with a usual-suspect AC locomotive's DC link, this is a technology I would consider.  The 'conventional' alternative would be to invert the third-rail DC to either powerline or alternator AC (depending perhaps on whether the locomotive were operating on catenary or diesel power) with the effective frequency information derived from that of the catenary or alternator source. 

Transformer-less boost converters were made with thyristors (SCR's) in the 1960's, s an example, the propulsion electronics for the BART trains acted as buck converters for normal propusion and boost converters for regeneration.

One advantage of using transformers for DC-DC conversion is to get galvanic isolation. For locomotives, this would allow use of something similar to a ground relay on the traction circuit on diesel-electric with DC motors.

For power levels used in locomotives, device choice is limited to GTO thyristors or silicon IGBT's. SiC FET's aren't quite there yet as far as current ratings for commercially available packaging Cree's top line SiC FET module is rated at 1200V/300A. Maximum switching speed for these devices at 800V/300A appears to be around 50 kHz, with the limit set by the module's heat dissipation rating. The higher switching frequency possible with SiC FET's should allow for outpt filtering of the inverter, which should not require the use of inverter grade motors.

- Erik

[nfotis]

Bethayres Sam

ahem, dc transformers are non-existant. If you want to raise dc voltage, you convert the power to ac And as we said in the Navy in Electrical and Electronics Prep School, "Don't sweat AC Battery Week!"

I do not remember the exact details, but in Europe locomotives have different transformers for AC or DC operation off the catenary (if my memory is correct, DC transformers are heavier than the AC ones).

Note that the catenary DC voltages typically encountered on European mainlines are 1500 and 3000 Volts (plus an amount of variation).

I do not know the details of wiring and related sub-systems for multi-system locomotives which can 'consume' both DC and AC voltages, but the weight difference is approximately three to four tonnes for the MS edition. You could ask Bombardier and Siemens for more details.

Regards,

N.F.

[nfotis]

Wizlish

A little more video with details of this rather interesting class:

Amusing to watch them tinker with those touchscreen UIs at nearly arm's length as the locomotive is moving ... and does that little repurposed rear-vision camera show the track that is hidden from view when the driver is seated?

Some notes:

These are *not* touch screens (see the buttons around each screen? These buttons control the user interface). The 3-4 screens cab arrangement is becoming the European standard.

The cameras are installed on coupler height (and there is a small light nearby), so the train driver can do easier switching without running from one cab to the other (only PESA has done this, so far).

There are also many locomotives in Europe sporting backward-looking cameras (usually high and near the cab doors), so you can watch the train trailing the locomotive while running. If you see various European cab rides, you might be able to see this in operation (if you want me to find one for you, tell me).

N.F.

[erikem]

nfotis

 Note that the catenary DC voltages typically encountered on European mainlines are 1500 and 3000 Volts (plus an amount of variation).

Some of the inverters used on European electric locomotives run directly off the 3kV DC catenary and use that as the DC link voltage when running off AC. By using an "inverter" instead of diodes for converting AC to DC, the locomotive has closer to a sin wave curent draw from the overhead and alo allows for regenerative braking.

The French were using 1500V for the DC link to enable running off of 1500V DC catenary as well as AC.

- Erik

[daveklepper]

but an electronic dc stepup of stepdown of voltage still is not really a transfomer which is defined by its use of inductive coupling, and square waves used in such stepup and stepdown can certainly be considered ac, just not sine-wave ac.  Similarly, the batteries used to store and regenerae ac are still dc batteries, with the ac resultng from educated switching and/or simple rectification on charging.

I think the market does exist for the through services mentioned, and they would make for more efficient use of Penn Sta. and  open up employment opportunities.   The LIRR has already expressed a desire to run to Riverdale, and stops serving Lincoln Center and the Columbia U. complex could simplify commutes for many.  The idea has been tested and works with the ballgame New Haven - Secaucus NJT-equipped specials.  It will be far more feasible when all catenary in the WAshington - Boston area is 60Hz, since MN New Haven div. mus don't like 25Hz.  Now if they had only kept the washboards!   Perhaps also the original M-2s?

[trackrat888]

Um,, just hook a eletric to a diesal? Then U have the problem of head-end power