3 ms·

https://en.wikipedia.org/wiki/Dynamic_braking#Rheostatic_braking https://en.wikipedia.org/wiki/Dynamic_braking#Rheostatic_bra... This specifically addresses th

https://en.wikipedia.org/wiki/Dynamic_braking#Rheostatic_braking https://en.wikipedia.org/wiki/Dynamic_braking#Rheostatic_bra... This specifically addresses the air brakes you're hearing: >Dynamic braking alone is insufficient to stop a locomotive, as its braking effect rapidly diminishes below about 10 to 12 miles per hour (16 to 19 km/h). Therefore, it is always used in conjunction with the regular air brake. This combined system is called blended braking.

Animats 8y ago
That's improved with AC locomotives. Regenerative braking now works down to zero speed, if desired.[1] Locomotive motors today are three-phase variable frequency synchronous motors, run as servomotors. Like other servomotors, they can be controlled all the way down to a stop. At some point the friction brakes are applied, but that's usually done only at slower speeds. Large modern locomotives often have "wings" with ventilation slots and fans. That's where the heat from the braking resistors gets dumped. This is a big win when moving heavy freight down long mountain grades. Friction brakes tend to overheat, but fan-cooled resistor banks can dump heat all day. It's amazing that semiconductors for that kind of power not only exist, but are not that big. [1] http://www.republiclocomotive.com/ac-traction-vs-dc-traction.html http://www.republiclocomotive.com/ac-traction-vs-dc-traction...