Siège avec vue
Stupid question: how does a #TGV or #AVE stop in the event of a power failure? Does the ABS have battery backup? Or do they just slam on the brakes and hope for the best?
Oct 21 at 3:32pmWeb
Show threadhelle 🐈 @ DHCP ☎️ 4355Oct 21

@siegeavecvue wonder if it does as we imagined, use the trick to determine phase difference with the overhead to notice outage, next step, it cannot regen and hence opens the main power feed, but does a regen brake to provide enough power to enable the eddy current brakes, etc to work

the rest of the control system has battery backups, but idk if that is actually viable for the eddy current brakes (it may just be)

Show threadhelle 🐈 @ DHCP ☎️ 4355Oct 21
@siegeavecvue but uh, worst case failure for just slam the brakes afaik is damaged brakes and rails, but otherwise a safe stopping
Show threadSiège avec vueOct 21
@helle Worst case failure being an Iberian Peninsula blackout, as the question came up during a conversation about that particular incident.
Show threadhelle 🐈 @ DHCP ☎️ 4355Oct 21

@siegeavecvue yeah, I meant more on the train side of things. Cab systems all run off of batteries by default. So any mode of braking is nominally controlled by the computer.

Ventilation, lighting, etc can run off of batteries (either by default or fail over), air conditioning tends to not, so there is a limit on how long a failed train can be before evacuation in weather extremes.

Show threadhelle 🐈 @ DHCP ☎️ 4355Oct 21
@siegeavecvue
Beyond that afaik every european highspeed train and most other trains are equipped with (suboptimal but present) self-evacuation equipment
Show threadbhtooefrOct 21
@helle @siegeavecvue this document talks about how the TGV Atlantique braking system works BTW: https://railroads.dot.gov/sites/fra.dot.gov/files/fra_net/14991/DOT-FRA-ORD-95-09-Safety%20of%20HSGTS-Technical%20Descriptions%20of%20Advanced%20Braking%20Systems%20for%20HSGT.pdf

if I'm reading this right, only the TGV M (Avelia Horizon) even has regenerative braking: https://www.railjournal.com/fleet/alstom-starts-production-of-100-avelia-horizon-trains-for-sncf/

everything else only has rheostatic (resistor grid) dynamic braking

and, yeah, if push comes to shove... train air brakes are *extremely* fail safe, the air pressure keeps them off, and if air pressure is lost, the friction brakes automatically fully apply under spring pressure
Show threadhelle 🐈 @ DHCP ☎️ 4355Oct 21

@bhtooefr @siegeavecvue so dynamic braking enabled by battery backup

the rest is good old electropneumatic with electrically controlled anti-wheel slip, that makes sense and that can also easily run off of battery

and yeah, we just recalled, TGV has neither permanent magnet or electromagnetic eddy current brakes

ICE3 does and it is one of the reasons why the french budget highspeed rail lines needed to be fixed before a decent train could run over them :P

Show threadhelle 🐈 @ DHCP ☎️ 4355Oct 21
@bhtooefr @siegeavecvue (there are actually like 4 different extra emergency brake solutions like Germany likes, in the matrix of lowered brake shoe on rail vs eddy current (suspended above even at application) and permanent magnet and electromagnet)