So, how much EMF from the transmitter 'escapes' the receiver in normal operation? It is this, I think, anyone who has concerns about the technology is effectively talking about. Whether any escaped energy can then cause problems with other devices is another matter. MW
On 19 Jul 2014, at 16:14, Peter C. Thompson via EV wrote: > You are correct. We are requiring 2-way communication as well as monitoring > of the power being transmitted. If some metal does come near/into the field, > the transmitter can easily detect this (big change in current) and shut down > the transmission. Likewise if the communication fails, power transfer stops. > If the alignment between pads shifts (we call it alignment check) outside of > nominal values, power transfer stops. If a living object comes near > (basically to the side of the car), power transfer stops. > > I've just spent an entire week working with the standard responsible for > this, so all of this is VERY fresh in my mind. :) > > Cheers, Peter > > On 7/18/14, 4:18 AM, Evan Tuer via EV wrote: >> It's more than improbable. There is 2 way communication with any of these >> wireless charging protocols, and monitoring of the power on both sides. >> Any rogue coil (which would have to be inserted pretty much in between the >> car and the charger whilst it is charging, which isn't going to happen >> accidentally) would cause a mismatch and transfer would stop immediately. >> >> Transfer won't start in the first place unless there's a correct, properly >> aligned and communicating receiver. >> >> >> >> >> On Fri, Jul 18, 2014 at 5:24 PM, Martin WINLOW via EV <ev@lists.evdl.org> >> wrote: >> >>> Hmmm, my instant reaction was 'extremely unlikely' as you would need a >>> 'receiver' circuit with the right resonant frequency to generate any sort >>> of significant energy. That said, it is, I suppose, quite feasible that >>> with the mass of coils of one sort or another that there are 'out there' >>> that some fluke of chance may just throw up a matching resonant situation >>> and then, who know's what could happen. It's a bit improbable though. >>> Certainly simple metal objects such as you mentioned will *not* be an issue. >>> >>> On the other hand, interestingly, the power used by the flux generating >>> coils in a large, whole body MRI scanner is about the same as that which >>> this inductive charger will use, ~7kW. As I suspect you know, these MRIs >>> come with all sorts of dire warnings about keeping metal objects out of the >>> way lest they turn into lethal projectiles. Fortunately, the MRI coils are >>> designed to do something completely different to the inductive charger and >>> so this issue is unlikely to be important. Also, the fixed coils energy >>> will only be 'live' when a car is charging so, again, it is improbable that >>> with the car in the way, anything would be able to get into a position >>> where something unexpected would occur. It will be interesting to see how >>> this all pans out. MW >>> >>> >>> On 17 Jul 2014, at 13:30, robert winfield via EV wrote: >>>> >>>> >>>> >>>> Wireless EV Charging on the Horizon, But is It Safe? >>>> >>>> >>> http://www.digitaltrends.com/cars/cables-needed-bmw-daimler-working-wireless-charging-technology-evs/ >>>> No cables needed: BMW and Daimler working on wireless >>>> charging technology >>>> for EVs >>>> By Andrew Hard — July 11, 2014 >>>> >>>> [image >>>> http://icdn2.digitaltrends.com/image/rsz_p90155654.jpg >>>> Wireless Charging Technology >>>> ] >>>> >>>> With the help of BMW and Daimler, electric vehicles are >>>> taking the next step >>>> toward worry-free ownership. >>>> >>>> The German automakers recently announced a joint effort to >>>> develop a >>>> wireless charging system for the i3 electric vehicle and i8 >>>> plug-in hybrid. >>>> >>>> EVs don’t need oil changes, filter replacements, or >>>> emissions testing, so >>>> they’re already extremely convenient to own. If the >>>> inductive wireless >>>> charging technology is viable, EV owners won’t even need >>>> to worry about >>>> refueling. >>>> >>>> BMW and Daimler’s charging tech works in the same way >>>> wireless cell phone >>>> chargers do, just on a larger scale. An alternating magnetic >>>> field transmits >>>> energy between two sets of coils: one mounted onto the >>>> car’s parking area >>>> (usually a garage floor), and a secondary coil on the >>>> vehicle itself. >>>> >>>> The array transmits energy at a charging rate of 3.6 >>>> kilowatts, which, >>>> according to BMW, is enough to fully charge an i8 in under >>>> two hours. The >>>> German engineers predict they can increase that rate to 7.0 >>>> kW in the >>>> future. >>>> >>>> The circular design of the coils comes in a compact, >>>> lightweight package >>>> that is equal parts subtle and slick. The floor-mounted >>>> baseplate will >>>> function even when exposed to rain and snow, and the car’s >>>> receiver coil can >>>> be activated with the push of a button. >>>> >>>> To keep the neighborhood cats safe and grounded, the current >>>> is >>>> automatically shut off if any foreign bodies are detected. >>>> BMW allows users >>>> to monitor the charging process with the i Wallbox and >>>> accompanying >>>> smartphone app. _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org For EV drag racing discussion, please use NEDRA (http://groups.yahoo.com/group/NEDRA)
