An effective common mode choke on the mains conductors should pass all
three conductors through the core. For a 2.4-inch OD core, three turns are
usually good. Too many more will increase the capacitive coupling. 31
material has an advantage at the lower frequencies where the older 43
material is a bit better at higher frequencies. All referring to HF.
I have "solved" many an emissions problem usually around 40 to 70 MHz from
SMPSs by simply installing a simple common mode choke on the mains lines
(yes, all three lines: hot, neutral, and "ground" - the green wire). Once
these products reach a contract manufacturer, the common mode choke adds
nothing to performance and only adds cost, so it is removed. Many times I
ran into the reality that contract manufacturers are the EMC engineer's
worst enemy. They are supplsed to retest and re-qualify, but they don't.
Dave - WØLEV
On Fri, Feb 18, 2022 at 10:51 PM Jim Brown <jim@audiosystemsgroup.com>
wrote:
> Thanks Ed. What ferrite mix and how many turns?
>
> 73, Jim K9YC
>
> On 2/18/2022 12:53 PM, Hare, Ed, W1RFI wrote:
> > We just obtained an AC line filter by Morgan Manufacturing. It also used
> > a ferrite on the ground wire.
>
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>
--
*Dave - WØLEV*
*Just Let Darwin Work*
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