1) I've preached wiring and PCB layout is not just DC, but high-frequency
as well - into the VHF and low UHF region. Transmission line concepts must
be considered. Consequently, good high-frequency practices must be
followed and employed. Happy to finally read this reflected by someone
else!
2) I've used the term "return" instead of "ground" for many decades as RF
energy does not really need "ground". I point out that the ISS does not
require "ground" to communicate via RF with our ground stations and that
the Crab Nebula does not need "ground" to fill space with copious amounts
of RF energy (as does the Sun as well). Glad to see the concept of
"return" advocated instead of "ground"!!
3) "BALUN" In amateur terms, what is it? The use of a CM choke totally
explains the concept. How many switching supplies have I brought into
compliance by simply adding the (eliminated for added cost) CM choke? Most
of them. And, yes, ALL wires (conductors) must pass through the choke.
Glad to see this finally proposed. And.......for amateur purposes, a
transformer in NOT a BALUN!!
Really glad to see these concepts taking traction, even if they are just
limited to our small group, here.
Dave - WØLEV
EMC Design & Test, LLC
On Mon, Jun 3, 2019 at 6:35 PM Jim Brown <jim@audiosystemsgroup.com> wrote:
> On 6/3/2019 9:21 AM, Hare, Ed W1RFI wrote:
> > There are a number of possibilities here.
>
> I got involved in trying to help a Solar Edge applications engineer
> optimize a couple of choke designs to be applied to the loop of
> optimizer outputs on the roof. He provided me with lengths of the cable
> they are required to use (by code). In the process, we had discussions
> at a couple of long lunches (he lives in Oakland, CA, about 70 miles N
> of me), and I made several major points to him.
>
> First, that the most cost effective way to solve these problems is to
> design the electronics to minimize MF and HF content, and to practice
> good EMC practices in mechanical/electrical product design. This would
> include interior layout of everything in the path of potentially noisy
> current, careful shaping of the switching waveform to minimize harmonic
> content (as first Elecraft, and subsequently Flex) have done with CW
> keying), and, of course, suitable filtering.
>
> Second, he described a bonding architecture for the panels in the
> particular installation in question whereby lightning ground and power
> ground were on opposite sides of the building, and said that had been
> dictated by the inspector. This arrangement could be producing both
> magnetic and EM fields. As part of troubleshooting, I suggested that the
> lightning ground temporarily be moved so that it follows the same path
> as the switched DC conductors.
>
> Noise generated by the panels themselves can, of course, be radiated by
> conductors within the panels, and by wiring external to the panels. In
> addition, the system can, if there is a sufficiently large loop, produce
> a magnetic field which can be quite strong in the near field. There are
> also electrical/mechanical designs that can minimize both the magnetic
> and EM fields.
>
> An example of what I'm getting at is careful implementation of
> microstrip techniques, either on circuit boards, or by routing
> conductors in very close proximity to a continuous conducting surface
> (like a metallic enclosure or frame). This causes return current to flow
> in the adjacent conducting surface, forming a transmission line, which
> in turn minimizes both the magnetic and EM fields.
>
> I've not heard from that systems engineer since my choke design was
> applied to the installation in question, but I've heard separately
> (perhaps here?) that they were redesigning some of their electronics.
>
> And, of course, there are multiple potential sources of EMI -- the
> panels, the optimizers, the inverter, and any control circuitry.
>
> > A common-mode choke is only going to be effective if it includes hot,
> neutral and ground for ac wiring and +, - and ground for dc.
>
> Exactly right. But for purposes of clarity of understanding, I prefer to
> use the word "return" in place of "ground" when talking about DC wiring.
> :) For the same reason, I don't like the word "balun" -- I can think of
> nearly a dozen VERY different things commonly described by that word, so
> using obscures understanding of what they are and how they work. :)
>
> Another point that I emphasized to that applications engineer was that
> it is NOT, DC wiring, it is, by virtue of the continuous switching of
> the waveform, both DC and RF wiring.
>
> 73, Jim K9YC
>
>
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>
--
*Dave - WØLEV*
*Just Let Darwin Work*
*Just Think*
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