Radio Noise from PV System

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Comments

  • boBboB Solar Expert Posts: 943 ✭✭✭✭
    Re: Radio Noise from PV System

    It will be interesting to see what Outback has to say about this.
  • inetdoginetdog Solar Expert Posts: 3,121 ✭✭✭✭
    Re: Radio Noise from PV System
    W0SD wrote: »
    I am disappointed by not surprised that I have RFI noise on amateur radio. I find a "birdie" about every 24 khz on all the amateur bands. I am using an Outback Flex 80. If I shut the breaker off to the four 205 watt 24 volt panels the "birdies" go away other than on 80 meters
    I can still barely hear them and if I shut the Flex 80 off then they go away. When the controller goes to "sleep" I of course do not have them.

    I have twisted the wires out of the controller going to the battery and I have tried ferrite all to no avail. I did some "sniffing" with my HT on two
    meters and I find the lines with about 50-60 volts coming in from the panel are radiating as well as those going to the battery bank. It would
    not be real hard to put the wires going to the battery bank in conduit but I wonder if anyone has had success doing this. I would assume you would have to bypass each end of the conduit to ground? It would be a lot more difficult to put the wire coming in from the panels in conduit. I have the first 25 feet buried.

    It is coming in over the antenna's as I can use antenna's farther away and the "birdies" are weaker and I can point my beans away and they
    get weaker.

    Another question? I note that the Xantrex MPPT controller has an FCC Class B rating. Is there anyone here that has this unit and could tune the ham bands and tell me if they have "birdies" They are very loud and are, not problem to hear from the Flex 80.

    Ed W0SD

    If you are seeing a birdie about every 24 KHz, it is an indication that it is related to a 24 KHz switching frequency in the DC to DC convertor of MPPT or the current regulation of PWM, with a very sharp edge that is generating lots of high harmonics.
    Some additional filtering inside the CC would be the best attack, but not really feasible without cooperation from the inverter or CC manufacturer. It is always easier to eliminate/reduce the source of the interference than to try to filter it out later. There is a tradeoff between a fast switching waveform to minimize losses in the switching element and a slower switching waveform to minimize harmonics.
    SMA SB 3000, old BP panels.
  • nielniel Solar Expert Posts: 10,311 ✭✭✭✭
    Re: Radio Noise from PV System

    this is interesting as to what this installer is saying, but i think he over thought it or he may have been misinformed. now longer wires will also increase inductance and nobody puts up warnings about not having wires too long due to the fets not switching properly. overcoming the resistive losses is a factor in long wire runs though. the inductance that is added is to affect frequencies far beyond what the desired frequency is (0hz) and the power content of those harmonics are much lower, especially in the rf spectrum range of things, so it will not have an adverse effect to the controller imo. we are NOT talking of very large amounts of inductance in the suppressing emi/rfi.
  • inetdoginetdog Solar Expert Posts: 3,121 ✭✭✭✭
    Re: Radio Noise from PV System
    niel wrote: »
    the inductance that is added is to affect frequencies far beyond what the desired frequency is (0hz) and the power content of those harmonics are much lower, especially in the rf spectrum range of things, so it will not have an adverse effect to the controller imo. we are NOT talking of very large amounts of inductance in the suppressing emi/rfi.

    Right, and since the goal is to stop harmonics from leaving the box at all, two measures to accomplish this would be:

    1. Use a co-axial capacitor (available for filtering automotive alternator noise) on both leads on the DC side, and
    2. A combination of a parallel capacitor to ground and a series inductor on AC leads. The inductor should be closest to the wire exiting the case and the capacitor should to from the outside end of the inductor to the neutral (not to the case ground.)

    Either of these should not be done except by a qualified electrician. A ferrite (with both hot and neutral or both + and - leads wound in the same direction though the same ferrite toroid if possible) is the only remedy which does not involve making a direct connection to any wires and is therefore DIY-safe.
    SMA SB 3000, old BP panels.
  • nielniel Solar Expert Posts: 10,311 ✭✭✭✭
    Re: Radio Noise from PV System

    a cap is one possibility and i agree some may lack the skills to wire up this simple part.

    as to adding the inductance, this is quite easy to do for any diy person. they don't have to use the donut types as any of these would suffice too,
    http://www.solar-electric.com/nosufefi.html
    also, it is possible to wind a coil out of insulated wire that would also add some inductance and this could be some of the wire already inline going to or from the cc. the thicker the wire the more difficult it may be to wind a tight coil, but larger coils can still add a tad of inductance. there's no law saying you can't run the + and - together in the same ferrite core either, be it a donut or otherwise, and if one can fit more turns of the wires to loop back through the ferrite material then they will gain even more inductance. in the case of just a couple of turns of wire and no ferrite material involved then the inductance produced by this will likely be too small to be effective at radio frequencies.
  • 54d1854d18 Solar Expert Posts: 63 ✭✭
    Re: Radio Noise from PV System

    I had pretty much the same issue with my Rogue MPPT,
    I added ferrites to the solar leads, but still no success, I then added
    a small, maybe 100 pF Ceramic Cap accross the solar leads and that
    pretty much did it.

    Lots of trial and error in my opinion.

    T
  • NorthGuyNorthGuy Solar Expert Posts: 1,925
    Re: Radio Noise from PV System
    54d18 wrote: »
    I then added
    a small, maybe 100 pF Ceramic Cap accross the solar leads and that
    pretty much did it.

    Cables usually have capacitance of about 15pF/foot. They're sometimes long. 50ft cable in my system gives me 750 pF.

    An that's, of course, not counting 100 mF of the controller's input capacitor :D
  • nielniel Solar Expert Posts: 10,311 ✭✭✭✭
    Re: Radio Noise from PV System

    54d18,
    when you placed the cap was the ferrite still in place? if so what do you observe when taking it out of line?
  • nielniel Solar Expert Posts: 10,311 ✭✭✭✭
    Re: Radio Noise from PV System

    north guy,
    the trouble with that wire capacitance is that it takes a long length of wire to achieve that desired capacitance and the capacitance does vary from wire to wire. the inductance and capacitance sets up a resonant point for what is basically now an antenna that is good for radiating the interference. now a capacitor can just change the resonant point and still be an antenna, but it may be in an area making the radiated energy you observed smaller as more is being attenuated. electrolytics do not always function well into the rf ranges so don't count on them for this purpose.
  • 54d1854d18 Solar Expert Posts: 63 ✭✭
    Re: Radio Noise from PV System

    Niel, the ferrites were and are still in place, when the
    noise dissappeared on the radio, I pretty much stopped.

    T
  • nielniel Solar Expert Posts: 10,311 ✭✭✭✭
    Re: Radio Noise from PV System

    remove any ferrites if it is easy to do and see if the noise increases. my point would be that it isn't just the cap working.
  • Scuba-JunkyScuba-Junky Registered Users Posts: 4
    Re: Radio Noise from PV System

    Which controller model? What end of the solar leads did you put the cap? Solar end or cc end of cable? Are you a ham radio op and if so, did this clean things up for the HF bands? What voltage is your panel array? What voltage is your battery system? I'm starting to think that all of these factors play into the equation.
  • VicVic Solar Expert Posts: 2,815 ✭✭✭✭
    Re: Radio Noise from PV System
    Which controller model? What end of the solar leads did you put the cap? Solar end or cc end of cable? Are you a ham radio op and if so, did this clean things up for the HF bands? What voltage is your panel array? What voltage is your battery system? I'm starting to think that all of these factors play into the equation.

    Hi SJ,

    Normally the first place to put emission reduction components is as close to the source of the emission generator as possible. In the case of an MPPT CC, this would be across the PV input terminals first. Lumped, rather than distributed capacitance if often the best. At times, placing ferrites and perhaps capacitor/s at the output terminals of the CC can help. Running power conductors in well-grounded, TIGHT metal pipe helps a lot.

    Believe that for the Classic CC to meet FCC B, the only addition that was required, from the initial design, was the addition a small amount of C at the PV input terminals. But, FCC Class B for devices like CCs applies only to frequencies at/above 30 Mhz. For HF enthusiasts, this leaves all frequencies of interest untested for emissions.

    Still, the best single remedy for RFI/EMI seems to be the separation of antennas from the Power Electronics, PV array/s, and unshielded power conductors, in my experience.

    FWIW, YMMV, Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
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