This year's snowpocalypse seems to be bringing the usual problems to electric traction systems; increased tension due to cold weather, ice buildup on conductors, etc. In good weather conductors on pantographs are subject to wear and need frequent replacement. Has anyone built a system where electricity is "harvested" from the caternary by electromagnetic induction without direct physical contact?
It could be doe, but somewhat educated guess is that it would add about an order of magntdue more cost to the overhead. "Somewhat educated guess" is from working on a contactless power transfer system.
It really is not possible. In essence, you are making an air core transformer where the primary loop is the caternary wire and the secondary loop would be a length of wire the total length of the train. Even with this, the efficiency of power transfer would be very poor at power line frequencies. That is why low frequency transformers have an iron cores. The iron core concentrates the magnetic flux around the wires. Out in the open air, most of the power would be lost. Furthermore, the caternary wire would need to be a closed AC current loop. You would source electric current into the caternary wire at one place and somehow it needs to return back to the original place to complete the loop. This would be a nightmare to design.
(Thanks a lot spell check)
NP Red Centenary wire"??? What is that? It really is not possible. In essence, you are making an air core transformer where the primary loop is the centenary wire and the secondary loop would be a length of wire the total length of the train. Even with this, the efficiency of power transfer would be very poor at power line frequencies. That is why low frequency transformers have an iron cores. The iron core concentrates the magnetic flux around the wires. Out in the open air, most of the power would be lost. Furthermore, the centenary wire would need to be a closed AC current loop. You would source electric current into the centenary wire at one place and somehow it needs to return back to the original place to complete the loop. This would be a nightmare to design.
It really is not possible. In essence, you are making an air core transformer where the primary loop is the centenary wire and the secondary loop would be a length of wire the total length of the train. Even with this, the efficiency of power transfer would be very poor at power line frequencies. That is why low frequency transformers have an iron cores. The iron core concentrates the magnetic flux around the wires. Out in the open air, most of the power would be lost. Furthermore, the centenary wire would need to be a closed AC current loop. You would source electric current into the centenary wire at one place and somehow it needs to return back to the original place to complete the loop. This would be a nightmare to design.
100 year old wire.
Norm
There are, as I recall, some transit systems using (or planning to use) an inductive method of power transfer, but I can't remember who or where. In their case, the power source is in the ground, between the rails.
I would opine that the apparatus to make this possible might be too cumbersome to elevate.
Larry Resident Microferroequinologist (at least at my house) Everyone goes home; Safety begins with you My Opinion. Standard Disclaimers Apply. No Expiration Date Come ride the rails with me! There's one thing about humility - the moment you think you've got it, you've lost it...
Larry, I believe that the use of coils in the ground is for charging batteries at fixed locations, not for continuous supplying power as a bus moves along.
Caternary, centernary=creative writing? I am of the opinion that "catenary" fits the bill.
Johnny
Norm48327 100 year old wire.
DeggestyLarry, I believe that the use of coils in the ground is for charging batteries at fixed locations, not for continuous supplying power as a bus moves along.
You're probably right - all I recall is that there's some inductive going on somewhere in the process. Seems like I did read of a plan that involved turning on the coils in the pavement at the car moved along, though.
But that does reinforce that doing so as an overhead would be problematic.
NP Red Furthermore, the centenary wire would need to be a closed AC current loop. You would source electric current into the centenary wire at one place and somehow it needs to return back to the original place to complete the loop. This would be a nightmare to design.
Furthermore, the centenary wire would need to be a closed AC current loop. You would source electric current into the centenary wire at one place and somehow it needs to return back to the original place to complete the loop. This would be a nightmare to design.
Could the power be fed to the wire for track 1 at point A, sent X miles to point B, and then be returned through the wire feeding track 2?
NP Red IIn essence, you are making an air core transformer where the primary loop is the centenary wire and the secondary loop would be a length of wire the total length of the train. Even with this, the efficiency of power transfer would be very poor at power line frequencies.
IIn essence, you are making an air core transformer where the primary loop is the centenary wire and the secondary loop would be a length of wire the total length of the train. Even with this, the efficiency of power transfer would be very poor at power line frequencies.
Yep. Power transfer would have to be done at higher frequencies. Efficient power transfer entails use of resonant coils on both the primary and secondary sides. The primary would almost certainly have to be segmented (think liner induction motor). Use of magnetic coupling and individualy powered primary segments would allow the primary to be placed at ground level if so desired, hence interest in streetcar applications where overhead wold be verboten.
Having said that, such a scheme would be a lot more expensive than catenary. Cost increasers will include dozens of multiple megawatt inverters per mile, lots of ferrite (eddy current losses in laminations start to get ugly at 400 Hz) and litz wire.
tree68 Deggesty Larry, I believe that the use of coils in the ground is for charging batteries at fixed locations, not for continuous supplying power as a bus moves along. You're probably right - all I recall is that there's some inductive going on somewhere in the process. Seems like I did read of a plan that involved turning on the coils in the pavement at the car moved along, though. But that does reinforce that doing so as an overhead would be problematic.
Deggesty Larry, I believe that the use of coils in the ground is for charging batteries at fixed locations, not for continuous supplying power as a bus moves along.
Might work - or in a parking spot, instead of having to hook up a cable...
But it seems like the application I saw had to do with moving vehicles (trolleys) and the coils being between the rails...
tree68 Might work - or in a parking spot, instead of having to hook up a cable... But it seems like the application I saw had to do with moving vehicles (trolleys) and the coils being between the rails...
Deggesty tree68 Might work - or in a parking spot, instead of having to hook up a cable... But it seems like the application I saw had to do with moving vehicles (trolleys) and the coils being between the rails... this more like what I remember seeing. It seems to me that this system is already in use somewhere--but I do not remember where.
this more like what I remember seeing. It seems to me that this system is already in use somewhere--but I do not remember where.
I think I remember a discussion about this a couple of years ago. If I remember right, it was in Europe or Israel, and it was in an experimental stage. I started rummaging back in the forum, but I lost interest after a while.
_____________
"A stranger's just a friend you ain't met yet." --- Dave Gardner
Could this be what we are looking for?
http://primove.bombardier.com/en/applications/tram.html
MidlandMikeCould this be what we are looking for?
Most likely.
While the system does chiefly run on batteries, I see that power transfer can be both static and dynamic, and besides places like stops, power would also be provided at "challenging sections," which I would presume to be grades or sections with long distances between stations.
MidlandMike Could this be what we are looking for? http://primove.bombardier.com/en/applications/tram.html
A similar system is being developed for electric cars, where the car is parked above the primary coil. It would be possible to place multiple multiple primary coils that would be activated when a secondary coil passes overhead.
OTOH, this bringing back memories of a book I read back in '77 titled YV88 and eco-fantasy of what Yosemite Valley could look like in 1988. One feature was a lot of electric light rail lines using two rail power and spring contacts to connect power only when the weight of a car was on it. Would be amusing to hear Mudchicken's take on that proposal along with the way the tracks were supported in the book.
erikemOne feature was a lot of electric light rail lines using two rail power and spring contacts to connect power only when the weight of a car was on it.
There are well-documented systems from GE that use intermittent contacts activated by electromagnet for the 'hot' supply (and running rails as the typical ground return, which is what you want). The pickup shoe completely shrouds the 'points' before activation, and spans at least two of them so there will be no interruption due to points, etc. (it is somewhat easier to arrange things with point contacts than with formal third rail). There are some interesting patents in the general period before our entry into WW1.
It's not that much more involved to 'code' the access to the electromagnet that turns the power on and off, so that little kids wanting a cheap thrill or cheap power can't just bridge or short things. Much more sophisticated than just a pressure switch!
If I remember correctly there is a good technical description of one of the GE versions in Burch's book.
This is a bit tangential but might be interesting.
The established alternative to overhead catenary is electrification using a third rail. The voltage for such systems is generally ~ 750 v, which is high enough to be lethal but low enough to limit the power that can be delivered to a train.
There have been systems which use some form of continuous protection (protecting the live rail from the weather and protecting people from electrocution). Protection of the live rail is only practicable with side or bottom contact. One such system, in operation from 1917 until 1991 (when it became part of a light rail network) between Manchester and Bury in England, used 1200 volts.
About a century ago an electrical engineer called Alfred Raworth proposed a four-rail system which would have used two protected live rails, one at +1500 volts, the other at -1500v, giving 3000v in total. Now, this voltage can deliver some serious power, or equivalently can radically reduce the number of substations needed. Since substations account for a big chunk of the cost of electrifying using conductor rails, large savings would have been possible if Raworth's scheme had been adopted. Unfortunately the railway which employed Raworth was merged with another which had a well-established 660 v suburban network so Raworth's plans were abandoned in the interests of standardisation.
For further information see the entry for Alfred Raworth in the following link:
www.steamindex.com/people/electrical.htm
Could Raworth's proposal - or something similar - be developed further today? Instead of steel conductor rails, porcelain insulators and wooden boards for continuous protection we would use stainless steel/aluminium conductor rails and silicone rubber for insulation. Raworth had to design his system around 1500v dc motors so there still had to be running rail earth return for dealing with small unbalanced currents in the two live rails. A modern system using power electronics could use the full 3000v and dispense with running rail return, which would avoid the need to remodel signalling track circuits (another big electrification expense).
There is now a wireless charging system available for a number of different electric cars made by different companies and its relatively inexpensive. A fri of mine has two Tesla model S's and after buying one system to try out on his wife's model S after three weeks he ordered a second on for his model S.
Talking with him last night at the coffee shop he stated his boss recently bought a model S and after he told his boss about the wireless charging system his boss ordered 10 of them and had them installed at work. They work great.
https://www.pluglesspower.com/shop/reserve-tesla-model-s/
In my opinion anything involving HVDC at ground level is a potential danger significant enough to reject it. I also suspect that the added capital expense of all the third rail and gap-filling (now with two-rail accommodation needed on locomotives for the gap filling accommodation, probably on top with a full potential difference between the pickups and leads) you'd be better off using overhead, perhaps one of the pickup schemes designed for modern trolleys that would have + and - DC and reference ground if needed in three separate conductors which the collector head keeps physically separate as it tracks.
I do think we are at the point where antenna fab and reliable high-frequency waveform generation has made good inductive charging practical for transit, and perhaps some 'heavy rail'. That's not a substitute in all cases for contacted current arrangemrnts, and the cost of batteries (or flywheels or whatever) for the trains and line side equipment has to be included.
in my not-so-humble opinion any new DC system over about 600V should be overhead, and alternatives to any exposed or energized conductor at ground level should be used (or even retrofitted).
The two interurbans that used high-voltage third rail systems were Michigan Railways and Central California Traction. CCT was moderately successful, but used a covered third rail and resorted to a fair amount of fencing (by interurban standards) on its rural sections. Although passenger service (except for Sacramento streetcar service) was discontinued in the 1930s, the third rail remained in use for freight until after WWII.
Michigan Railways tried 2400 volts before settling on 1200. MRy equipped (human) conductors with bars to drop on the third rail and running rail to trip substation breakers in the event of an arc struck with one of the car journals. For safety during the 2400 volt period, all stations had high level platforms with what amounted to chutes for the passengers to board.
Blackcloud 5229 There is now a wireless charging system available for a number of different electric cars made by different companies and its relatively inexpensive. A fri of mine has two Tesla model S's and after buying one system to try out on his wife's model S after three weeks he ordered a second on for his model S. Talking with him last night at the coffee shop he stated his boss recently bought a model S and after he told his boss about the wireless charging system his boss ordered 10 of them and had them installed at work. They work great. https://www.pluglesspower.com/shop/reserve-tesla-model-s/
The article below discusses a number of systems that dispense with overhead wires:
http://www.railengineer.uk/2012/11/28/trams-without-wires/
RME In my opinion anything involving HVDC at ground level is a potential danger significant enough to reject it. I also suspect that the added capital expense of all the third rail and gap-filling (now with two-rail accommodation needed on locomotives for the gap filling accommodation, probably on top with a full potential difference between the pickups and leads) you'd be better off using overhead, perhaps one of the pickup schemes designed for modern trolleys that would have + and - DC and reference ground if needed in three separate conductors which the collector head keeps physically separate as it tracks. I do think we are at the point where antenna fab and reliable high-frequency waveform generation has made good inductive charging practical for transit, and perhaps some 'heavy rail'. That's not a substitute in all cases for contacted current arrangemrnts, and the cost of batteries (or flywheels or whatever) for the trains and line side equipment has to be included. in my not-so-humble opinion any new DC system over about 600V should be overhead, and alternatives to any exposed or energized conductor at ground level should be used (or even retrofitted).
the New York Central railroad uses to this day 660 volts DC under running third rail covered with wood as an insulator to prevent train and engine employees from getting electrocuted. Worked out of Grand Central Terminal for several years and it still works well. Not bad for a system designed by GE and put in service around 1903 as the city passed an ordinance to the laminate operation of all steam locomotives in NYC. Back the the original substation was still in operation 6 stories below ground level 6 motor generator units to produce 660 DC for the trains which were finally replaced with solid state converters to eliminate the use of the original generators. The originals last I knew are still there just no longer used as it isn't worth the effort to remove them.
Blackcloud 5229 ... Not bad for a system designed by GE and put in service around 1903 as the city passed an ordinance to the laminate operation of all steam locomotives in NYC...
... Not bad for a system designed by GE and put in service around 1903 as the city passed an ordinance to the laminate operation of all steam locomotives in NYC...
The ordinance was for Manhattan Island. Some steam continued to operate in all the other 4 boroughs. Even on the west side freight line had steam into the 30s.
What would that do to my pacemaker or Insulin Pump on my hip?
CandOforprogress2What would that do to my pacemaker or Insulin Pump on my hip?
Nothing; it's DC.
Of course, if you stepped wrong and shorted the DC across your lower body, the resistive heating might cause some localized damage to the pacemaker, increase the impedance at the embedded electrodes due to cooking, and perhaps denature the insulin in the pump reservoir.
RMEOf course, if you stepped wrong and shorted the DC across your lower body,
If you stepped wrong and shorted 600 VDC at a gazillion amps across your body, I suspect a malfunction in your pacemaker or insulin pump would be the least of your troubles.
tree68If you stepped wrong and shorted 600 VDC at a gazillion amps across your body, I suspect a malfunction in your pacemaker or insulin pump would be the least of your troubles.
Whooooooooosh!
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