From: Peri Hartman via EV <[email protected]> >It says, "Usually, electromagnetic brakes require a constant power >supply to be held open." It seems they presume that most EV >manufacturers are using some sort of electromagnetic brake, where the >brake is tensioned to the closed position with a spring and held open >with an electromagnet. (I guess if there's a brake system failure, >you'll have full-on braking.)
I've never seen this type of brake, except in industrial vehicles and trains. Has anyone ever seen an on-road EV that had this kind of "normally on" brakes? The closest thing I can think of are parking brakes, which can be either on or off without power. >I would think that most EVs have cable brakes. Parking brakes may work that way; but every EV I've seen has still had a fully hydraulic braking system. My guess is that automotive regulations (added 100 years ago, to ban unreliable mechanical brakes) may require them. On whether an EV's regenerative braking can bring the car to a stop: This is a software issue. If the designers want to, the controller can "regen" right down to zero, or even cause the car to then move backwards. Below some speed, you won't get any power from regen (the system's idling power is greater than the braking energy), but the motor controller can still generate torque in either direction right through zero RPM. -- Excellence does not require perfection. -- Henry James -- Lee A. Hart http://www.sunrise-ev.com _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub ARCHIVE: http://www.evdl.org/archive/index.html INFO: http://lists.evdl.org/listinfo.cgi/ev-evdl.org Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA)
