> From: Lee Hart <[email protected]> > > "wireless charging" is fundamentally just a transformer.
With an extremely lossy core! It's been decades since I worked in RF engineering, but they don't change the laws of physics very often. Electromagnetic coupling between two coils depends on the frequency of the signal being propagated, proximity of the coils, and permeability of the material between the coils. All three factor seem to be challenged in rapid-charging EV batteries. Frequency is at odds with high currents, which means larger conductors, which has a "skin effect" at higher frequencies. Proximity is an obvious problem with contactless charging, unless one coil is inserted into another, which sorta loses the main advantage of "contactless." And the permeability of iron is about 1,000 times more than that of nitrogen (the major component of air), which is actually an inhibitor — you're better off using a vacuum than nitrogen! So, how does modern "contactless" high-power charging work? Seems like an intractable design problem to me! I'm guessing it involves "contact" between hefty iron cores at moderate frequencies. But I admit, I don't know. Jan _______________________________________________ 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)
