/"//Is there any inherent advantage or disadvantage to non transformer
inverters? /
//
///Jay"/
Well, non-isolated transformer-less inverters have their own problems
that can make common-mode EMI worse actually than isolated.
There are special (and patented) design techniques to reduce this and
some non-patented ones that work similarly. I think SMA is one
with a patent on it. It has to do with how the output stage of the
inverter does its shorting of the full-bridge in-between high and low
PWM pulses. Interesting stuff.
But engineering is always a compromise. Audio electronic engineering
was MUCH easier than power electronics IMO.
boB
On 10/3/2020 8:01 AM, Dave Angelini Offgrid Solar wrote:
I would think if the devices meet the tested Class B spec then no
advantage. Engineers can design filters for the Class B requirement.
The radiated RF may be different between two identical specced
inverters of different topology. Even that can be designed in, if
there is a requirement and it is tested for.
The basic test anyone can do is with a 10 dollar analog AM radio tuned
to a weak station. If you can't get 5 feet back from the inverter and
hear the station, then you have work to do to suppress the radiated
garbage. An XW is about 3 feet if it is installed correctly. My truck
inverter which is transformerless, will kill AM for about 50 feet.
See what Bob says, my component level engineering is from the 1980's
and dated.
*Dave Angelini Offgrid Solar "we go where powerlines don't"
http://members.sti.net/offgridsolar/ e-mail [email protected]
<mailto:[email protected]> text 209 813 0060*
On Fri, 2 Oct 2020 11:58:15 -0600, Jay <[email protected]> wrote:
Hi Bob
Is there any inherent advantage or disadvantage to non transformer
inverters?
Jay
On Oct 2, 2020, at 11:27 AM, "[email protected]"
<[email protected]> wrote:
This is all great advice.
Remember that long wires can radiate RF. PV lines and the array can
make a good antenna for RFI as well as the battery lines.
I agree with Dave that both of those inverters are more than likely
similar. I know that the XW has a good filter on the battery line
right where it should be, at the exit point.
An additional ferrite toroid core used in common-mode filter hookup
(BOTH hot and cold wires run through the center) as close to
the unit as possible on AC and DC wires as well as possibly,
communications lines exiting the units. Battery temperature sense also,
possibly.
As for resources, Palomar link that Roy gave is a good resource.
Digikey or Mouser might also be a good place to look for both the
parts themselves and possibly information.
boB
K7IQ
On 10/2/2020 8:57 AM, Dave Angelini Offgrid Solar wrote:
My advice is it is more about the installation and the distance
from the inverter, and it's devices from the station location, than
the make of equipment. There are other things also that I do to fix
noise and interference. My wife is an extra class operator and
several clients have visited to get ideas. Most any noise issue can
be fixed later, unless you are too close to the source.
That said I mainly use XW and I would assume Radian is similar.
Below is the spec that XW is test for and has been since 2005.
" EMC directive FCC and Industry Canada Class B " Below are 2 of
the ways that the issue is defined and measured.
So-called "*radiated emissions*" are picked-up *with
a* test-antenna and can come from all parts of the product
INCLUDING the cables it uses (power and module interconnects).
*Conducted emissions* are measured directly as voltages or currents
on the cables used by the product.
*Dave Angelini Offgrid Solar "we go where powerlines don't"
http://members.sti.net/offgridsolar/ e-mail [email protected]
<mailto:[email protected]> text 209 813 0060*
On Fri, 2 Oct 2020 09:35:34 -0600, Mac Lewis <[email protected]>
wrote:
Hi Wrenches,
I have a HAM radio enthusiast that needs to replace their
off-grid inverter. He would like the inverter that puts off
the least interference. I don't know a whole lot about
evaluating an inverter for this, but I am reaching out for
recommendations. Needing ~8kVa at 48V.
Thanks!
--
Mac Lewis
"Yo solo sé que no sé nada." -Sócrates
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