Qualcomm Idiot Claims No More Loss From Inductive Charging Than Wired  - Page 1
Forum section: electronics / general

author: Sionyn
author_rank: Frequent Contributor
timestamp: August 23, 2012, 04:26:08 pm
content: bit misleading on power induction

author: Pat Pending
author_rank: Regular Contributor
timestamp: August 23, 2012, 06:47:11 pm
content: Transformers a built on the principle that a closed path highly permeable core allows the flux to flow in a loop and thereby link the isolated coils together with least loss.There are already enough inefficiencies dues to heating and saturation for example, so it seems somewhat counter intuitive to insert an under the car air-gap into the magnetic path.that said ---The permeability of air is 1.00000037 (u/u0), whereas wood is 1.00000043 (u/u0).Heck, filling that air gap with a massive pile of newspapers would boost the efficiency of the Qualcomm system

author: shg
author_rank: Newbie
timestamp: August 26, 2012, 01:21:04 pm
content: The inductive charging can be very efficient, the ~95% they get IIRC is quite possible.The key aspects are the coupling and heat/radiation loses.If your resonant circuit has a high quality factor (Q), then you don't have to have a high coupling factor (the amount of stream lines passing through the receiver coil divided by the total number of stream lines). Also the coupling factor at distances less than or comparable to coil diameter (which we can see here) yield a reasonable coupling factor (like 0.1 or more).The loses are mainly due to the resistance of the coil multiplied by the Q factor, as there is more power circulating in the resonant circuit than it's being delivered at a single time instant. To overcome this you just have to decrease the current and increase the voltage. That's the case with free-running circuit. A loaded circuit will display a heavy drop at the Q factor, and now a resistive losses due to transferred power are dominant, that's exactly the same with transformers.If we are on the transformers, the purpose of the core is to provide high permeability to achieve high inductance which minimises resistive losses at low frequency (no-load current, etc.), and provide additional coupling when the circuit is loaded (you need a tight coupling in a low frequency transformer to lower the inductance of the primary to allow more current to pass through). The resonant transformer is a completely different case.And as the last one - radiation losses. Those are quite small if the circuit is designed to be a bad antenna (obviously you don't want to radiate the energy), and yet, most of the energy can be withdrawn from the system if a receiver is placed at a very short distance.Google for wireless power transfer, there are some papers in which they (I mean the authors, not Qualcomm) claim 85% efficiency in a very small circuit at high distance (compared to the coil diameter) and high frequency (like 100 MHz). Or see this one:http://www2.lns.mit.edu/fisherp/83.pdfThey've achieved 90% efficiency at 1 m with 0.6 m diameter coil, good enough for a car.For a general consumer 95% efficiency is virtually the same as no losses at all, and yes, it is possible.

author: ciccio
author_rank: Frequent Contributor
timestamp: August 26, 2012, 03:29:43 pm
content: I'm not an expert, so I cannot give any technical opinion on the subject, but I really disliked the post title : "Qualcomm Idiot..".I don't think that a Company like Qualcomm will charge an IDIOT to give a public presentation of something that can be. in the future, a real "money factory" for them.In any case I watched the video and, maybe because of my limited English, have not seen or heard anything the could allow you to define an IDIOT the Qualcomm' reperesentative.Best regards

author: G7PSK
author_rank: Super Contributor
timestamp: August 27, 2012, 12:13:47 pm
content: It was the interviewer who was just short of a load rather than the interviewed Qualcom representative. The Interviewer was asking a question getting an answer and coming up with something else as the answer.