I don’t see 100 V/m. Assuming an omni pattern, 0.5 W peak power and using,
E = √(30•ERP) / r the phone would need to be within a few centimeters of the observation point, and in that close the distance scaling assumption in that equation breaks down. -- Ken Javor (256) 650-5261 From: "doug emcesd.com" <d...@emcesd.com> Reply-To: "doug emcesd.com" <d...@emcesd.com> Date: Tuesday, July 25, 2023 at 6:53 PM To: <EMC-PSTC@LISTSERV.IEEE.ORG> Subject: Re: [PSES] Woodgate's reply on residential Immunity field strength Hi All, My observation is that a cell phone at max power, close to the product, generates voltages and currents in the product that are on the order of what a 100 V/m far field would induce! I have seen many manifestations of this including making a product permanently non-functional. Interestingly enough, the design feature within that product that caused the issue was ground fill on a circuit board that was resonant in the upper cell phone band. Pretty easy to find with signal injection into the structure. These kind of problems are easily found using a coaxial dipole. Here are a few links: https://emcesd.com/tt2006/tt020106.htm https://emcesd.com/tt2010/tt080410.htm As with ESD, using the standards based test setup for troubleshooting these kind of problems is very inefficient. Once a problem occurs, I build a custom way of injecting signals, like the above, and find the problem very quickly. In this case, one just needs a signal source of appropriate power and the coaxial dipole. An interesting bit of my history. These days we think 10 V/m is dangerous. But when I was 15, I played for hours at a time with a device I made that generated a continuous signal at 300 kHz of 10,000-20,000 V/m and I am still here! I was developing 600 Watts of power from a pair of 811A power triodes oscillating at 300 kHz to feed the resonant Tesla coil structure I built. The effects were pretty amazing, lighting up fluorescent tubes 4-6 feet away to full brilliance with no wires and even incandescent bulbs would light in the vicinity, held in my hand! Pieces of metal nearby got hot from induction heating. I did lots of crazy technical things when I was 12-18 years of age. By the way, those 811A tubes above (the “A” versions had cooling fins on the plates) were powered from a 3B28 xenon gas rectifier tube and had 1500 V and at more than half an Ampere available on the plate caps. Enough to kill one rather quickly, but I knew what I was doing back then and survived to write this. Doug From: Charlie Blackham <char...@sulisconsultants.com> Sent: Tuesday, July 25, 2023 0:06 To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] Woodgate's reply on residential Immunity field strength The residential level of 3m V/m was in IEC 1000-4-3 predates portable phones, WiFi, Bluetooth and all the other mobile and portable transmitters widely in use today. The 20+ V/m field strengths in these standards are what is obtained from a cellular phone at maximum power, or WiFi device, at approximately 0.3 m / 1 ft. Now, on live networks the 99% percentile transmit power of a cell phone is around 1% of maximum power, but that’s not considered in safety standards such as SAR testing Best regards Charlie Charlie Blackham Sulis Consultants Ltd Tel: +44 (0)7946 624317 Web: https://sulisconsultants.com/ Registered in England and Wales, number 05466247 From: Brian Gregory <brian_greg...@netzero.net> Sent: Monday, July 24, 2023 10:49 PM To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] Woodgate's reply on residential Immunity field strength The reference for 20 V/m to EV chargers comes from UL 2231-2. This is not a medical standard, but Annex A does call out the medical standard 60601-1-2 as a reference, as well as CENELEC 50204. We can't figure out why; cell phones produce less than half that, and our WiFi transmitter is probably representative, and is rated well under 1 W. I could see a higher immunity standard as needed for commercial environments, say in a bank of 4-5 chargers. Following along in 61000-4-3, we agree with John that residential applications are clearly best matched to the definition for Class 2 environment, and the table in Clause 5 says the limits for Class 2 equipment is 3 V/m. 20 V/m does not show up in Clause 5 of 61000-4-3 for any class. So, I've should to reach out to a UL standards group and find out if this is really necessary for residential applications. Our local lab can't do more than 10, and an overseas affiliated lab is similarly limited. I'd like to know were this requirement comes from. This is more a question for EV Charging safety than a mainstream EMC question. As a backup, I could request a comment to Ken's point is if they define the peak of the modulation as 20 V/m. I don't know where these are defined. Thanks for all the detailed replies! Colorado Brian 720-450-4933 ---------- Original Message ---------- From: John Woodgate <j...@woodjohn.uk> To: Brian Gregory <brian_greg...@netzero.net> Subject: Re: [PSES] Immunity test field strength, residential setting Date: Fri, 21 Jul 2023 18:05:59 +0100 61000-4-3 is a Basic Standard. It does not specify test levels but indicates possible test levels. You need to look in detail at Clause 5, but look at these words: Product committees shall select the appropriate test level for each frequency range needing to be tested as well as the frequency ranges. The residential environment is usually designated Class 2 (see Annex E of the standard), which calls for 3 V/m. ====================================================================================== Best wishes John Woodgate OOO-Own Opinions Only www.woodjohn.uk Rayleigh, Essex UK I hear, and I forget. I see, and I remember. I do, and I understand. Xunzi (340 - 245 BC) On 2023-07-21 17:44, Brian Gregory wrote: Hello colleagues, We are building EV Chargers for residential markets (not just US) and one of the safety applicable standards is UL 2231-2. It calls out IEC 61000-4-3 for immunity testing parameters, which states a requirement for a field strength of 20V/m. Our EMC expert says typically testing is "done at 3 Vrms, which is standard for most products in residential environments." He can only test up to 10V, and we're hearing the same from an overseas lab to whom our manufacturer refers. Does FCC Part B have guidelines for field strength we can cite? Can some offer this "DC guy" (aka, 60 Hz) a quick definition of what the 20V/m represents? I'm guessing 20 V/m is for higher density commercial applications, aka charging stations, so we probably need an exception for residential. Thank you! Colorado Brian 720-450-4933 This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. 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