Dear Michael,
Thank you for your clear and specific reply to my question.
I will investigate whether residual RFI continues when microinverters are
shut down.
Best regards,
Michael, W9IP
From: Michael Carter <Mike.Carter@unh.edu>
Sent: Tuesday, January 03, 2023 1:26 PM
To: RFI@contesting.com; nlsa@nlsa.com
Subject: Re: [RFI] RFI when solar array is switched off?
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@contesting.com
<mailto:rfi-bounces+mike.carter=unh.edu@contesting.com> > on behalf of
nlsa@nlsa.com <mailto:nlsa@nlsa.com> <nlsa@nlsa.com <mailto:nlsa@nlsa.com>
>
Sent: Tuesday, January 3, 2023 12:19 PM
To: RFI@contesting.com <mailto:RFI@contesting.com> <RFI@contesting.com
<mailto:RFI@contesting.com> >
Subject: [RFI] RFI when solar array is switched off?
CAUTION: This email originated from outside of the University System. Do not
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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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