Talk:Regenerative brake

From Wikipedia, the free encyclopedia

Trains Portal

This article is within the scope of WikiProject Trains, an attempt to build a comprehensive and detailed guide to rail transport on Wikipedia. If you would like to participate, you can visit the project page, where you can join the project and/or contribute to the discussion.

[edit] Relation with hybrid

Among confusions about the hybrid cars, many seem to believe that hybrid is mainly to allows regenerative breaking ? It is not. Hybrid is one way to avoid the lost of efficiency of powerful piston gas engine when running at low power, the Quasiturbine photo-detonation engine being one other possibility. Regenerative braking energy recovery is insignificant on the highway, little when the battery are near fully charge, limited to soft breaking (heavy breaking exceeding recovery power capability), and none for now from the back wheels (still waste energy to standard friction brakes) http://www.hybridcars.com/renerative-braking.html . It is however valuable in intense city driving, and is also of course an asset of most hybrid concepts. Regenerative braking system can also exist independanty from hybrid. City driving car energy use is shown at : http://www.fueleconomy.gov/feg/atv.shtml Gilles

I would have thought that was obvious.. ? But regenerative breaks are easier (cheaper) to impliment in vehicals that are normally driven from a source of electricity (rather than gasoline or something) - IE hybrids or electric cars. Of course, if one made the ability for a gasoline car to be run by a battery then it could use regenerative brakes - but it would become a hybrid in the process. Regenerative brakes could be used to charge a car's battery (which isn't used for propulsion), as the braking energy is simply energy that can be used anywhere. Maybe note of this needs to be made in the article. Fresheneesz 20:00, 30 May 2006 (UTC)

[edit] a couple of train related questions

1: i was under the impression that rehostatic breaking rather than friction breaking was used if there was nowhere to put the regenerated power. 2: i presume deisel electrics still generally rely on rehostatic breaking (though i've heared a few are now using batteries) is this correct?

Primary train brakes are almost universally air brakes (occasionally electropneumatic). These are of course friction brakes.
Locomotives universally (except for very early on) have friction brakes on their wheels. Normally straight air brakes, although steam brakes were often used on steam locomotives. N.B. The term for locomotive brakes is "independent brake" (said brakes can be controlled independently of the automatic or train brakes). BDD
The vast majority of electric and diesel-electric locomotives have rheostatic braking available as well. (this is "dynamic braking" in US railroad parlance). Railroaders like this because it does not wear or heat up the friction brakes, and applying more braking from the locomotive causes the train's slack to bunch up, allowing for an easier time once a rise is encountered again.
A small number of electric locomotives have regenerative braking. This generally requires direct current electrification; alternating-current regenerative braking requires the locomotive's generation to be 'in phase' with the supply.

Hope that helps. Matthew Brown (Morven) (T:C) 23:23, 7 May 2006 (UTC)

[edit] dynamic brakes

Dynamic brakes should probably get their own section, since theres significant discussion about them - and as of right now, the explantion and definition are badly placed. Fresheneesz 20:00, 30 May 2006 (UTC)

I added some dynamic braking material to the Diesel-electric article. On further thought, I'm wondering whether there's enough detail to justify a separate article. Dynamic braking is a natural outgrowth of Diesel-electric propulsion, so it is really a subsystem of the overall package. Bigdumbdinosaur 17:03, 18 February 2007 (UTC)

[edit] References needed

This article currently has no sources for its information, so I've tagged it as {{unreferenced}}. We need these not only to back up the statements made but to expand on them to provide some details. For instance, there is no real information about how regenerative brakes came to be. The article currently says they are "descended from dynamic brakes", but there is no separate article on the latter. The earliest date is a vague "mid-20th century", by which time the ancestors of these brakes were already implemented in trains, etc. Clearly there must have been more history than this. Does anyone have some sources for these details? Thanks. ~ Jeff Q (talk) 09:20, 10 June 2006 (UTC)

I have added some cross references with other articles to describe the history, but sources are still needed. ~ Bryan 19:50, 23 Aug 2006 (UTC)

[edit] Clutter

I think the current regen braking article is cluttered and somewhat disorganized. References to dynamic braking should be eliminated, as they are not germane to the article (except clarification should be kept to indicate that dynamic and regenerative braking are not the same). Bigdumbdinosaur 17:06, 18 February 2007 (UTC)

I'll try to find references for my facts but for now they come from professional knowledge. I'm not sure about the US, but in the UK Rheostatic braking is distinct from dynamic braking. Rheostatic braking being the dissipation of braking energy through resistor grids. As stated regenerative braking returns the generated current back to the line to be used by an accelerating train in a nearby section or back to the supply grid. Research and development continues into acceptable methods of energy storage.

The traction supply may not always be receptive to regenerated current and so in most practical applications a regenerative braking system also has the ability to use Rheostatic braking. Dynamic braking describes such a system. Three of the London Underground Rolling Stock uses dynamic braking 92TS (Central Line), 95TS (Northern Line) and 96TS (Jubilee Line). The system used by the 92TS is known a Dynamic Blending. As electrical brake is ineffective below 10mph the use of the friction brake has to be blended in as the electrical brake cannot maintain the demanded deceleration rate. The 92TS has motors driving every axle and so dynamic braking can be employed at every position. The 95TS and 96TS, however have either 2 and 3 trailer cars respectively in the train formation. These trailers don't have motors and so cannot brake electrically. The system used on these stocks are known as Cross Blending. The braking control unit measures braking rates for each car and for the unit as a whole and balances the braking from the electrical and friction brakes. The electrical brake in used in preference.

The big benefit of regenerative braking is for urban railways and metros where the trains have a short journey time between stations 2 to 3 minutes on London Underground. Regenerative braking metros around the world can safe up to 45% of traction energy requirements.

As I say I don't have references for this that are available in the public domain, but I hope this help to direct the arguement. If am able to find public domain references I will add.

Retrieved from "http://en.wikipedia.org../../../r/e/g/Talk%7ERegenerative_brake_99e0.html"

Categories: Start-Class rail transport articles | Unknown-importance rail transport articles