Through the magic of switchgear and electrical engineering, the traction motors become generators, just like dynamic braking on a diesel-electric (some non-regenerative electrics also had DB).
The difference is that instead of the electricity being dissipated as heat through a resistor bank (essentially a big toaster), it is fed back to the overhead lines, just like a small power plant feeding into the electricity grid.
Others can better explain in technical terms exactly how this works, and the differences between DC and AC electrifications.
Greetings from Alberta
-an Articulate Malcontent
.. and were it not for a lower than 100 % degree of electric efficiency the feedback would not account for 50 % of the energy taken from the wire for up-hill work but all of it.But even this way electric traction is and always was the most efficient of all modes and that goes together with 3 - 5 times superior power output per engine mass - that's why I wonder how it could be the American RRs with 6000 - 8000 ihp steam locomotives went diesel with 900 - 1010 motor hp - uhm - units and put four, six or eight upfront. In other words, they bought four to eight units for one straight electric because that 'straight electric' and wiring would have cost the same as three diesels. AND - they would not have to confront the pollution theme now or in the next future.Suddenly they couldn't count straight anymore?
Juniatha
A bit of DC motor theory: The voltage developed on the motor armature is proportional to the product of the applied magnetic field and the rotational speed of the armature. If the voltage applied to the armature is higher than the voltage generated by the armature, current will flow into the armature and the motor will generate torque (i.e. act as a motor). If the voltages are equal than no current flows and no mechanical power is generated. If the voltage on the armature is higher than the applied voltage, current will flow out and the motor is now acting as a generator. That it it absorbs mechanical power and turns it into electrical power.
The Milwaukee electric locomotives used DC series motors, which complicates regeneration. The locomotives had a high current low voltage generator that would be connected to the motor fields and that would then turn the motor into a generator. A similar thing is done in diesel electric locomotives where a current is applied to the traction motors to turn them into generators.
The trick for AC motors is a little bit different, where frequency is used to control whether the motor is motoring or generating. An unloaded 4 pole induction motor will run at almost 1800RPM on 60Hz, if you connect it to an engine running at 1850RPM, the motor will now act as an induction generator.
Juniatha .. and were it not for a lower than 100 % degree of electric efficiency the feedback would not account for 50 % of the energy taken from the wire for up-hill work but all of it.But even this way electric traction is and always was the most efficient of all modes and that goes together with 3 - 5 times superior power output per engine mass - that's why I wonder how it could be the American RRs with 6000 - 8000 ihp steam locomotives went diesel with 900 - 1010 motor hp - uhm - units and put four, six or eight upfront. In other words, they bought four to eight units for one straight electric because that 'straight electric' and wiring would have cost the same as three diesels. AND - they would not have to confront the pollution theme now or in the next future.Suddenly they couldn't count straight anymore? Juniatha
+1
Capitol costs of electrifecation. Engine changes unless 100% electrified.
But:
Erik_MagThe trick for AC motors is a little bit different, where frequency is used to control whether the motor is motoring or generating. An unloaded 4 pole induction motor will run at almost 1800RPM on 60Hz, if you connect it to an engine running at 1850RPM, the motor will now act as an induction generator.
These are all synthesis drives, which are reconfigured to produce (often via filtered-DC intermediate link, as for traction synthesis) the HVAC with correct phase. This is two separate steps: modulation/control of the motor fields, and synthesis of the power sinewave at grid frequency.
In any case the phase issue that was so difficult in the '40s can be solved by the same approach used for distributed generation: the grid sine wave itself can be used as a synthesis reference or amplified and shifted to use as field excitation. Even in dual-mode lite the detection of frequency can be done effectively by non-contact means before the pan is fully raised to contact.
Interesting info..... thanks everybody.
Yeah, i can imagine, circa 1950, the thought of "Electrifying" all those Thousands and Thousands Of Miles of usa railroads made diesel VERY Attractive
daveklepper Capitol costs of electrifecation. Engine changes unless 100% electrified.
Isn't there some maintenance cost involved with it, too?
If GM "killed the electric car", what am I doing standing next to an EV-1, a half a block from the WSOR tracks?
I remember that the DM&IR was considering electrifying the long steep grade from their yard up on the plateau above Duluth, down to the ore docks. The did a study and found a greater return on investment in 2-8-8-4s than in electrification. I would guess it was for similar reasons that electrifications in North America were virtually confined to tunnel projects and urban areas.
Operationally a three unit Diesel - electric - Diesel has many advantages. Run the 2 diesels on mostly flat lands and use the CAT powered units on grades. That may put approximately14,000 HP on grades ( 4 - 6 - 4 ) and 8000 for flatland operation. You have minimum fuel consumption, less carbon output and reduced wear and tear on the 2 diesel prime movers. Also fewer enroute fueling stops.
RRs would save much costs for the electrifications as the need for CAT would only be on the main lines. CAT only needed for heavy HP requirements. Yard tracks would not need CAT for train make up. The RRs would need short pocket tracks with CAT for silent lay overs of diesel equipment.
If there was a train coming up grade the same time another was going down grade the 3 units going down grade could provide both regeneration and the electric power from the diesels to provide enough kilowatts to the upgrade train. That is just one possible way of several that operation could be implemented.
Overmod But no one uses AC motors directly connected to the line for locomotive traction any more -- especially not for single-phase catenary.
But no one uses AC motors directly connected to the line for locomotive traction any more -- especially not for single-phase catenary.
But of course...
In order to understand how a variable voltage variable frequency drive operates, one must first understand how a rotating field motor operates with a fixed frequency source. The one mental adjustment needed for motor design is that with a variable frequency design, there is no need to provide high torque at high slip, so an induction motor can be designed for maximum efficiency (i.e. low slip) and not have to worry about starting torque. The low slip feature aids with adhesion as just a small increase in wheel speed will result in a significant reduction in motor torque.
Take Dave's picture and add 1 or 2 battery tenders that gets charged when on CAT or in DB ..
rdamonTake Dave's picture and add 1 or 2 battery tenders that gets charged when on CAT or in DB
But also note that where there's catenary there can be loads of wayside storage, including KERS for prompt high-current storage that is then used 'over time' to charge systems with lower standby loss.
Issues with having to 'use a train going downhill to power one going uphill' haven't been relevant since before the turn of the century (when the initial improvements in magnetic storage were publicized).
That's not to say there isn't a future for large onboard battery/supercapacitor architecture. But the packaging, weight and servicing, cost, and potentially restricted cell life, and some of the safety considerations of massive mobile batteries with high energy density remain significant. There is also the concern of strategic or 'politically-affected' material in certain battery technologies with massive alternative technologies competing for supply.
kenny dorham Interesting info..... thanks everybody. Yeah, i can imagine, circa 1950, the thought of "Electrifying" all those Thousands and Thousands Of Miles of usa railroads made diesel VERY Attractive
So much so that sometime after the war the PRR considered de-electrifying their lines from New York to Washington and Harrisburg.
Long story short, they ran the numbers and decided to leave things as they were, which in the long run worked out so much better.
blue streak 1 Operationally a three unit Diesel - electric - Diesel has many advantages. Run the 2 diesels on mostly flat lands and use the CAT powered units on grades. That may put approximately14,000 HP on grades ( 4 - 6 - 4 ) and 8000 for flatland operation. You have minimum fuel consumption, less carbon output and reduced wear and tear on the 2 diesel prime movers. Also fewer enroute fueling stops. RRs would save much costs for the electrifications as the need for CAT would only be on the main lines. CAT only needed for heavy HP requirements. Yard tracks would not need CAT for train make up. The RRs would need short pocket tracks with CAT for silent lay overs of diesel equipment. If there was a train coming up grade the same time another was going down grade the 3 units going down grade could provide both regeneration and the electric power from the diesels to provide enough kilowatts to the upgrade train. That is just one possible way of several that operation could be implemented.
Even in a situation like that, a railroad would still be rostering a relative handful of electrics to provide additional power under short stretches of catenary. It would be an additional expense above and beyond those of the primary diesel roster for little real advantage.
IIRC, much (maybe all) the juice for the MILW came from hydro-electric plants. I seem to remember an option when another train wasn't coming upgrade that the regenerative generated power from one going down grade was used to power pumps to refill the reservoirs (it's called "pumped storage") as you generally can't store the massive amounts of electricity involved - they don't make capacitors that big and the massive cost of that many lead-acid batteries ruled that out The other alternative was big banks of resistors at the substations instead of being on board the power.
Overmod
beaulieuObviously there is switchgear and Tap Changers involved, but the input to the traction motors is still 16.7Hz AC and at least in the Swiss case the locomotives are capable of regenerative braking.
It was interesting to see how PRR proceeded, or chose not to proceed, with power development on the 25Hz system from the late Thirties. I believe any development of 'universal' motors ended in the early '50s, with the rectifier experiments earlier; this even though the vast wartime expansion of the system west to Pittsburgh (described in detail in 1943) completely involved 428A motors (as in the DD2 and supposedly far superior to the 627s in the GG1s).
You are talking complications and batteries and diesel / electric combinations. All these are but loop ways and detours around the straight and forward solution to that one problem: get rid of that outdated diesel traction and turn to the future! American RRs have lost decades lingering in the 1940s when diesels were glorified to them by GM as clean and modern and they swallowed the message not taking a second look: diesels never were clean and they never were the future. Now you twist and bow about how to get a change without leaving the diesel behind for good and without having to invest fully in electrification.
Just imagine such a battery monster derailing and falling down the embankment - what an environmental mess this creates! Outright fantastic!
You will take so long until compelled to act by government laws - and then you complain!
O-M-G!
beaulieu "Obviously there is switchgear and Tap Changers involved, but the input to the traction motors is still 16.7Hz AC and at least in the Swiss case the locomotives are capable of regenerative braking" German (DB), French (SNCF) and Austrian (ÖBB) electrics have also had regenerative braking since a long time. I think other countries have it, too. It is nothing special over in Europe. =J=
BEAUSABRE IIRC, much (maybe all) the juice for the MILW came from hydro-electric plants. I seem to remember an option when another train wasn't coming upgrade that the regenerative generated power from one g0oing down grade was used to power pumps to refill the reservoirs (it's called "pumped storage" as you generally can't store the massive amounts of electricity involved - they don't make capacitors that big and the massive cost of that many lead-acid batteries ruled that out). The other alternative was big banks of resistors at the substations instead of being on board the power.
IIRC, much (maybe all) the juice for the MILW came from hydro-electric plants. I seem to remember an option when another train wasn't coming upgrade that the regenerative generated power from one g0oing down grade was used to power pumps to refill the reservoirs (it's called "pumped storage" as you generally can't store the massive amounts of electricity involved - they don't make capacitors that big and the massive cost of that many lead-acid batteries ruled that out). The other alternative was big banks of resistors at the substations instead of being on board the power.
Well, let's start with your "IIRC". You don't. Where would this tiny thing be? You could not pay for such a thing in a hundred years considering the tiny amount of electricity involved.. Where? You have to have a convenient and drastic change in elevation at the right place. So show us these lakes and dams that did this. Otherwise forget the fantasy. The "train going downhill provides power for the train going uphill" was a PR dream. Did the train going uphill sit and wait for a downhill ? Think about this and you might realize why electrification was a failure.
Overmod It was interesting to see how PRR proceeded, or chose not to proceed, with power development on the 25Hz system from the late Thirties. I believe any development of 'universal' motors ended in the early '50s, with the rectifier experiments earlier; this even though the vast wartime expansion of the system west to Pittsburgh (described in detail in 1943) completely involved 428A motors (as in the DD2 and supposedly far superior to the 627s in the GG1s).
IIRC, the last locomotives with 25 Hz series motors built in the US were a pair of circa 1952 GE demonstrators that were ran on the GN, VGN, NH and PRR with the PRR eventually taking possession. The contemporary Westinghouse locomotives used ignitron rectifiers with DC traction motors.
The choice of 25 Hz power for US electrifications can be traced back to the original Niagara Falls hydroelectric plant as plants were intended to provide power for motors as opposed to lighting. This became a standard for utilities that supplied power that would be converted to DC for street railways, interurbans, aluminum smelters and DC distribution (Edison system).New Orleans has a 25Hz power plant for their drainage pumps - the pumps run at low speed and a 25 Hz motor is more efficient than a 60 Hz motor.
The original testing of AC series motors was done at 60 Hz, and the consensus was that 10 hp was the largest series motor that could be run on 60 Hz. Westinghouse (B. G. Lamme) then worked on 25 Hz motors with much better results. A lower frequency is better, one reason why Europe went with 16.67 Hz and the SP experimenting with 15 Hz on the Visalia Electric.
The modifications needed to make a series motor work on AC results in a motor that is more expensive to and less efficient than a DC motor of equivalent power.
Juniatha You are talking complications and batteries and diesel / electric combinations. All these are but loop ways and detours around the straight and forward solution to that one problem: get rid of that outdated diesel traction and turn to the future! American RRs have lost decades lingering in the 1940s when diesels were glorified to them by GM as clean and modern and they swallowed the message not taking a second look: diesels never were clean and they never were the future. Now you twist and bow about how to get a change without leaving the diesel behind for good and without having to invest fully in electrification. Just imagine such a battery monster derailing and falling down the embankment - what an environmental mess this creates! Outright fantastic! You will take so long until compelled to act by government laws - and then you complain! O-M-G! Juniatha
You have to realize... The Class 1's have studied electrification over the decades and the results generally are positive.. Cost is a challenge, but it's not the main obstacle. The Class 1's are looking for a partner to help them invest and electrify their mianlines. I do see it in the future. Some sort of PPP could just be the way to electrfiy the nations trunk lines.
SD60MAC9500 Juniatha You are talking complications and batteries and diesel / electric combinations. All these are but loop ways and detours around the straight and forward solution to that one problem: get rid of that outdated diesel traction and turn to the future! American RRs have lost decades lingering in the 1940s when diesels were glorified to them by GM as clean and modern and they swallowed the message not taking a second look: diesels never were clean and they never were the future. Now you twist and bow about how to get a change without leaving the diesel behind for good and without having to invest fully in electrification. Just imagine such a battery monster derailing and falling down the embankment - what an environmental mess this creates! Outright fantastic! You will take so long until compelled to act by government laws - and then you complain! O-M-G! Juniatha You have to realize... The Class 1's have studied electrification over the decades and the results generally are positive.. Cost is a challenge, but it's not the main obstacle. The Class 1's are looking for a partner to help them invest and electrify their mianlines. I do see it in the future. Some sort of PPP could just be the way to electrfiy the nations trunk lines.
This is more years ago than I care to admit to, but an article in Railway Age said that the sticking point was demand charges for electricity -- the idea that the railroad would pay varying amounts for electric power depending on the time of day or other circumstances.
The railroad executives did not like the idea of the variable cost of electricity being yet another constraint on dispatching trains.
As to "cost not being an obstacle" yet the railroads looking for a "partner" to "invest", who is that partner supposed to be?
If this investment pencils out a positive rate-of-return, at least in the case of BNSF, who has deeper pockets than Mr. Buffett?
Paul Milenkovic SD60MAC9500 Juniatha You are talking complications and batteries and diesel / electric combinations. All these are but loop ways and detours around the straight and forward solution to that one problem: get rid of that outdated diesel traction and turn to the future! American RRs have lost decades lingering in the 1940s when diesels were glorified to them by GM as clean and modern and they swallowed the message not taking a second look: diesels never were clean and they never were the future. Now you twist and bow about how to get a change without leaving the diesel behind for good and without having to invest fully in electrification. Just imagine such a battery monster derailing and falling down the embankment - what an environmental mess this creates! Outright fantastic! You will take so long until compelled to act by government laws - and then you complain! O-M-G! Juniatha You have to realize... The Class 1's have studied electrification over the decades and the results generally are positive.. Cost is a challenge, but it's not the main obstacle. The Class 1's are looking for a partner to help them invest and electrify their mianlines. I do see it in the future. Some sort of PPP could just be the way to electrfiy the nations trunk lines. This is more years ago than I care to admit to, but an article in Railway Age said that the sticking point was demand charges for electricity -- the idea that the railroad would pay varying amounts for electric power depending on the time of day or other circumstances. The railroad executives did not like the idea of the variable cost of electricity being yet another constraint on dispatching trains. As to "cost not being an obstacle" yet the railroads looking for a "partner" to "invest", who is that partner supposed to be? If this investment pencils out a positive rate-of-return, at least in the case of BNSF, who has deeper pockets than Mr. Buffett?
I can only imagine how 'demand pricing' would have worked for electrified railroads in Texas during the recent freeze where a normal $40 bill became $9000.
Never too old to have a happy childhood!
The very utilities you mentioned and the USDOT. Perhaps some other private instruments as well. It's going to take a coordinated effort.
SD60MAC9500 Paul Milenkovic SD60MAC9500 Juniatha You are talking complications and batteries and diesel / electric combinations. All these are but loop ways and detours around the straight and forward solution to that one problem: get rid of that outdated diesel traction and turn to the future! American RRs have lost decades lingering in the 1940s when diesels were glorified to them by GM as clean and modern and they swallowed the message not taking a second look: diesels never were clean and they never were the future. Now you twist and bow about how to get a change without leaving the diesel behind for good and without having to invest fully in electrification. Just imagine such a battery monster derailing and falling down the embankment - what an environmental mess this creates! Outright fantastic! You will take so long until compelled to act by government laws - and then you complain! O-M-G! Juniatha You have to realize... The Class 1's have studied electrification over the decades and the results generally are positive.. Cost is a challenge, but it's not the main obstacle. The Class 1's are looking for a partner to help them invest and electrify their mianlines. I do see it in the future. Some sort of PPP could just be the way to electrfiy the nations trunk lines. This is more years ago than I care to admit to, but an article in Railway Age said that the sticking point was demand charges for electricity -- the idea that the railroad would pay varying amounts for electric power depending on the time of day or other circumstances. The railroad executives did not like the idea of the variable cost of electricity being yet another constraint on dispatching trains. As to "cost not being an obstacle" yet the railroads looking for a "partner" to "invest", who is that partner supposed to be? If this investment pencils out a positive rate-of-return, at least in the case of BNSF, who has deeper pockets than Mr. Buffett? The very utilities you mentioned and the USDOT. Perhaps some other private instruments as well. It's going to take a coordinated effort.
I believe in the Railway Age article, the power utilities were offering to string the catenary. But the power would be sold on the same terms as to other, large industrial customers where there would be a demand charge. That was a no-sale for the railroads because that would impact their dispatching and their line capacity.
I see that variable costs are a negative factor to RRs. Yet, aren't diesel fuel costs also fluctuating according to the price of oil, the marke situation, tax percentage and possibly other influences?
I feel RRs are maybe expecting a special price because they are so vital to the business traffic of the nation and they are already so hard struck by .. competition with trucking companies etc?
In Europe a hindrance in developing more powerful steam locomotives was that they tend to ask higher mainentance expenditures - it was not seen that an engine of 150 % the power of an earlier one may rightly demand 150 % higher maintenance costs and be no less efficient. In France, in the case of the Chapelon engines this was turned against these powerful engines. In Germany the 'arguement' was turned against each effort to (properly) develop a large eight coupled express engine and it always remained the Pacific that what chosen right to the final design (DB class 10 / DR 01-5). Or, with the 44 class Decapod against the 45 class Lorraine type (2-10-2) of ~2000 versus ~3000 ihp the latter was considered 'costly' at some 120 % the maintenance costs of the former - contorted thinking.
That thinking seems to repeat here with diesel ./. electrics..?
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