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)
100 year old wire.
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, 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.
South Shore’s catenary was getting close to that age when it was replaced recently.
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.
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?
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.
This could possibly be worked for private vehicles–you stop over the coil, send an identifying message to the charging system, which then charges your battery–and charges you for the joules?
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.
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.
Could 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.
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.
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 deali