[RFI] Impedance at 60 hz
jim at audiosystemsgroup.com
Fri May 22 12:00:22 EDT 2015
On Fri,5/22/2015 8:28 AM, Aaron Kreider wrote:
> How close is the impedance at 60 hz for material 31 to zero?
> I want to filter the inputs and outputs to my 5000 watt solar inverter
> with ferrite chokes, and I'm wondering if there is any risk of
The output of that inverter is not only 60 Hz -- if it produces RF
noise, it's because it has strong square wave components. If you add
inductance in series with individual conductors, you will round off
those square waves, which is likely to increase the dissipation in the
switching devices, which could overheat them and cause them to fail. The
same is true of charge regulators. Trying to filter these components can
be like putting lipstick on a pig. Why not buy stuff that is RF clean in
the first place?
We do not have an overheating problem if we wind all three conductors
through a common mode choke, because the net current through the core is
quite small (that is, the current in the phase conductor is cancelled by
the current in the neutral). The problem with that is that conductors
rated for 40A (I'm assuming 120VAC) can't be wound multiple turns
through a ferrite core. If it's 240VAC, you might manage an effective
choke with #12 conductors, which are rated for 20A. For that choke, use
both phases and green.
If you already own this beast, a better solution is a good line filter,
properly installed. That means zero length leads, including a zero
length bond between the shielding enclosure of the filter and the
shielding enclosure of the inverter.
It's also a good move to run all pulsed currents in twisted pairs. This
minimizes radiation from the differential component of the current.
73, Jim K9YC
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