http://www.northeast.railfan.net/images/gm1976a.jpg
- Paul North.
EDIT: *"Critters" are usually small low-HP industrial locomotives by oddball, specialized, or very small volume manufacturers, such as Plymouths, Whitcombs, etc. - see http://www.railroadinfo.com/critter-definition.html The GM10 fits none of those criteria, and is pretty much the exact opposite - hence the correction. - PDN
An electric motor is rated very differently than an internal combustion engine. A motor rated at "1000 hp" is rated to produce this for a certain amount of time. If it is rated at this for 1 hour, it may actually be capable of 2 or even 3 times that amount of power for shorter durations. I assure you that a traction motor rated at 1000 hp is capable of far more than that but not full time.
ICLandInterestingly, the modern AC traction motor diesel-electric will likely reduce the costs of Electrification if and when railroads ever get around to it, ironically by lowering the costs of the motive power and permitting the use of high voltage DC overhead instead of AC, since the inverters to take advantage of a DC supply system are already built into the off-the-shelf AC diesel-electric. The use of high voltage DC will significantly reduce the physical cost of the building the overhead.
Interestingly, the modern AC traction motor diesel-electric will likely reduce the costs of Electrification if and when railroads ever get around to it, ironically by lowering the costs of the motive power and permitting the use of high voltage DC overhead instead of AC, since the inverters to take advantage of a DC supply system are already built into the off-the-shelf AC diesel-electric. The use of high voltage DC will significantly reduce the physical cost of the building the overhead.
Locomotive inverters typically run off an 800VDC bus, which is too low for heavy electrification. Components are currently (pun not intended) available that would allow inverters to run directly off a 3,000VDC catenary, but that's also too low for long haul electricfications.
Having said this, AC traction motor technology would make it cheaper to produce new freight electrics as the power conversion (e.g. transformer) only needs to provide a constant voltage feed to the inverter as opposed to variable voltage and current supply needed by DC traction motors.
fredswain An electric motor is rated very differently than an internal combustion engine. A motor rated at "1000 hp" is rated to produce this for a certain amount of time. If it is rated at this for 1 hour, it may actually be capable of 2 or even 3 times that amount of power for shorter durations. I assure you that a traction motor rated at 1000 hp is capable of far more than that but not full time.
A few months ago I asked about this here to try to get a better handle on quantifying that overload capability, and some members were kind enough to provide detailed information. Of course, ''it all depends'' on the locomotive, motor specs, the particular service and environmental conditions = outside air temperature at the moment, etc. Nevertheless, to summarize as best as I can recall - without going back and looking it up, a doubling of the power output could not be sustained for longer than 5 or 10 minutes, and a 10 or 20 percent increase might be OK for a half-hour to an hour, but not longer.
Also, this applies to 'universal' = series-wound DC motors and similar = commutator AC motors only, I believe*. I don't believe it applies to AC induction motors, which are 'self-limiting' as I understand it.
*I'm not an electrical engineer, and have no pretensions of being one, so if I'm wrong or less than complete or correct with any of this, anyone who knows the subject better please feel free to jump in with comments and corrections, etc.
erikemLocomotive inverters typically run off an 800VDC bus, which is too low for heavy electrification. Components are currently (pun not intended) available that would allow inverters to run directly off a 3,000VDC catenary, but that's also too low for long haul electricfications.Having said this, AC traction motor technology would make it cheaper to produce new freight electrics as the power conversion (e.g. transformer) only needs to provide a constant voltage feed to the inverter as opposed to variable voltage and current supply needed by DC traction motors.
The newest European electrics are using a 6Kv DC link. That is why their performance under a 3Kv DC overhead is less than on any AC overhead.
If the energy is recaptured, and there is no other train on the system to use that energy, what's the point or feeding back into the catenary besides dynamic braking? And, when there is no other load, how is the load dissipated in the catenary when going downhill?
Link is to an E60C running at TXU's Martin Lake Tx Line: http://www.trainweb.org/southwestshorts/txue60.html
They have three of these former NdeM RR electrics which were for an electric line in Mexico whic was never built. They also are reported to have GE U23B's for Ash Train Duty, and maybe even some former BNSF C30-7's on the property.
At the Montecello, Tx plant and Lignite mine they have some E25B's running as well:
http://www.trainweb.org/southwestshorts/txue25bmonticello.html
As one of the previous posters pointed out, a European practiced mirrored in these electric operations is the use of single electric motors on their trains. their operations run 24/7 and apparently enjoy a high reliability on their utilizations.
Link here is to the SouthWest railfan site for the TXU Montecello Operation:
http://www.trainweb.org/southwestshorts/txumonticello.html
This link is to the same SWRF website for the TXU Martin Lake Operation:
http://www.trainweb.org/southwestshorts/txumartinlake.html
Link to the same fella's 'Southwest Railfan' web page on the Black Mesa & Lake Powell, which is another operation that uses 6,000 HP GE E60-type electric locomotives, but at 50 KV instead. At something like 78 miles, it's also much longer than any of the others referenced above:
http://www.trainweb.org/southwestshorts/bmlp.html
Thanks for those links, Sam - I'd seen some of these photos of the BM&LP before, but I don't know that I ever saw the whole web page and description, etc. He also has a list of several other webpages on misc. rail operations, at -
http://www.trainweb.org/southwestshorts/home.html
Where does the energy dissipate when fed back into the catenary?
I recently learned that the WMATA Metro dynamic braking feeds into wayside battery cabinets but I understand that to be capacitor cabinets, as there was no real way to feed the energy back into the third rail. Either that or super-powerful fans blowing on resistor grids under the rail cars.
I'd really like to know the reality of dynamic braking into catenary and third rail. It sounds untrue for energy saving.
Recall that electric railroads use purchased power, and that if there is no train on the line the power can be returned to the grid for general use.
Interesting, I didn't think of feeding it back to the utility. I wonder if the hydro dams on the NEC feed their surplus to the utility.
But hold on, at least with the NEC, do they really feed 25 Hz back to the utility? Doesn't that need a dedicated set of converters?
aegrotatio Interesting, I didn't think of feeding it back to the utility. I wonder if the hydro dams on the NEC feed their surplus to the utility. But hold on, at least with the NEC, do they really feed 25 Hz back to the utility? Doesn't that need a dedicated set of converters?
The way regenerative braking is handled is simple in concept but takes some high power management and now electronics. 25Hz 12Kv is the nominal power settings for the NEC. Any train "A" load on the system (actually various segments) will lower the voltage. The regenerative braking system on train "B" will try to increase the voltage back to 12Kv +. If the voltage goes above ( some value that I've forgotten maybe 12.9Kv) the regenerative eases off and dynamic brakes on the loco or even dynamics on Silverliner Vs and other EMUs take over. Then when CAT voltage goes down -- back to regenerative. This switching back and forth can be almost instantaneous.
Some power converter stations (use motor generator sets or solid state TRs) and also the hydro generator stations can also feed power back to the 60Hz grid when the voltage goes up.
The ebb and flow of load and regenerative power of many different trains is a management nightmare especially on the out of date PRR NEC electric grid. It takes a deft hand and lots of electronics. The NH-BOS section is probably much easier to manage.
If you think loco dispatch is hard imagine a power desk if things do not go as planned or programed when something in the grid breaks!! And Amtrak has to co-operate with SEPTA as well even though the 2 systems are mainly separate. NJ Transit's 25KV is separate but can have the same problems. One Amtrak Power desk is at 30th St.
Thanks, Blue Streak, this is exactly the kind of answer I was looking for.
Our community is FREE to join. To participate you must either login or register for an account.