[RFI] RFI when solar array is switched off?

David Eckhardt davearea51a at gmail.com
Tue Jan 3 14:52:10 EST 2023


Would it be possible for your installer to accompany you on a visit to a
recent installation?  It can't hurt to ask.  Take the appropriate equipment
to assess the RFI with you on the visit.

Dave - WØLEV

On Tue, Jan 3, 2023 at 6:25 PM Michael Carter <Mike.Carter at unh.edu> wrote:

> Hi Michael,
>
> All inverters, whether centralized or distributed (microinverters
> on each module of the PV array) have an accepted input
> voltage range over which they will perform the DC to AC conversion.
> If the inverter's input DC voltage falls below the low end
> of the range, it will shut down.  However, the PV module
> I-V curve exhibits only moderate changes in terminal voltage
> with large changes in irradiance of the module, and the
> inverter(s) may not shut down even with low irradiance
> levels (think early morning and late afternoon when sun
> angles are shallow relative to array inclination).  Both
> centralized and distributed inverters with Maximum Power
> Point Tracking (MPPT) have an additional constraint on the
> range over which MPPT is possible.  In that sense, the array being
> 'off' is not defined by the PV module terminal voltage
> but by the inverter's design specifications.
>
> The RFI potential of various inverters/microinverters has been
> discussed at length on this forum - it's important to
> discuss with your prospective PV system installer which
> system architecture (centralized vs. distributed inverter)
> and equipment brands they customarily use before committing
> to purchase.
>
> Can one shut off inverters?  For a central inverter, certainly via
> the array disconnect switch.  For distributed inverters - maybe.
> Some microinverters are compliant with the Rapid Shutdown
> requirement (for UL listing of such equipment as well as
> NEC 2020) and both AC and DC sides of the microinverter
> can be disconnected remotely.  Whether there is any
> residual RFI generation in that state is an open question.
> A mains disconnect switch is a requirement for any
> PV system, but as others on this forum have noted the
> primary mode of inverter RFI is via radiation from the PV
> array wiring rather than the AC mains.
>
> In short, discuss your concerns with prospective PV
> system installers and bring the installers' responses
> back to this forum.
>
> 73,
> Mike, K8CN
> ________________________________
> From: RFI <rfi-bounces+mike.carter=unh.edu at contesting.com> on behalf of
> nlsa at nlsa.com <nlsa at nlsa.com>
> Sent: Tuesday, January 3, 2023 12:19 PM
> To: RFI at contesting.com <RFI at contesting.com>
> Subject: [RFI] RFI when solar array is switched off?
>
> CAUTION: This email originated from outside of the University System. Do
> not click links or open attachments unless you recognize the sender and
> know the content is safe.
>
>
> Dear friends,
>
> I have a question about the "off" state of PV arrays.  If a solar array
> generates RFI when it is on, does it stop when the array is turned off?
>
> I suppose that the answer depends on several factors:
>
> *       type of array (string inverter vs microinverter)
> *       definition of "off"
> *       mains disconnect status
>
> I'm asking because my family is considering a pretty big array.  I don't
> know in advance whether its RF emissions will be troublesome to my 2m EME
> system but I assume the worst.  However, if I can throw a switch that
> RF-silences the solar array while I'm operating, then the problem
> disappears..
>
> Thanks -
>
> Michael, W9IP
>
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-- 
*Dave - WØLEV*


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