Why is an electromagnetic driveshaft retarder not the same as regenerative braking?
You’re not missing anything. The drivers are wrong. They know how to drive, but they don’t understand electromagnetism. An electromagnetic retarder is, effectively, a generator. Exactly as in hybrid vehicles. But because hybrid technology is still in its infancy, the generated energy has so far just been burned off (literally, via radiating circuits) rather than harnessed to charge a battery. Regenerative braking is most beneficial in stop-n-go traffic, so we are starting to to see hybrid buses and urban delivery trucks. The main issue with hybrids though is that they are complicated — with electric motors at each wheel as well as the main engine, a very heavy battery pack, and sophisticated electronics to control everything. The other issue is that long-haul trucks spend most of their time being driven at moderate, steady speeds on highways, so in the big picture hybrid propulsion wouldn’t have such a big impact.
To clarify, in the Telma system, the kinetic energy goes to waste, and the mechanism for braking happens to use extra energy. In a regenerative braking system, the kinetic energy goes to the battery, and there is no extra energy required. The analogous system for regenerative braking would have two electromagnets instead of one permanent magnet and one electromagnet, and you would drive current through one of the electromagnets.
Wow.. I’m getting confused. 1. Telma retarder -> using eddy currents induced by a rotating magenetic field to generate heat. Magnetic field is set up using electromagnets for easy on/off switching. (So it’s not always running). 2. Regenerative braking in a hybrid. There is an electric motor somewhere in the system (I’m not sure if it’s at the wheels or on the drive shaft, doesn’t really matter. When you rotate the rotor on an electric motor, you will generate a current if there is a circuit. This circuit is hooked into the battery, so you have just turned your electric motor into a generator (crappy efficiency, but hey, a little bit of recovered energy!). The telma retarder could in theory be set up to do the same thing, recover energy and send it to the truck battery. It wouldn’t do much good though, because the truck isn’t in a position to really use that energy, you could reduce the load on the alternator a bit, but you’re not in a position to use that power to drive the truck (beca
I’m kind of late to the party here, but to me it’s pretty simple: – Magnetic braking and regenerative braking both convert mechanical energy into electrical energy, via conductive things turning inside magnetic fields (or fields turning inside conductive things). – Magnetic braking creates this electrical energy in a solid metal rotor, which is basically a short circuit that turns all the energy into heat. The electrical energy cannot be recovered from this type of brake. – Regenerative braking creates this electrical energy in a coil of wire, so it can be sent to a battery, capacitor, back into the power line, etc. – Electromagnetic braking requires power from the vehicle because it uses electromagnets to create the magnetic field for the brake rotor to spin inside. It’s done this way to make it easy to control. Magnetic braking can also be done with permanent magnets and controlled by moving them closer or farther away from the rotor. This requires no external power at all. – Regener
