Agree start with data so you know where go On Sat, Jul 1, 2023, 9:20 AM Kirk Herander via RE-wrenches < re-wrenches@lists.re-wrenches.org> wrote:
> I'm going to first obtain access to an oscilloscope to characterize and > screenshot this phenomena, both before and after any mitigation I do. > > On Fri, Jun 30, 2023 at 12:46 PM bob--- via RE-wrenches < > re-wrenches@lists.re-wrenches.org> wrote: > >> >> >> We are talking to Kirk offline about this but the main issue here is that >> the enclosure >> for the 2000A combiner is made out of steel which is ferrous. That means >> that when the >> 120 Hz ripple current induces into the chassis it can vibrate just like a >> transformer. >> >> Low frequency transformer inverters are have higher ripple than the newer >> HF transformer units >> but they have some AC ripple on the battery cables as well. >> >> This combiner is evidently been around for about 8 years and we haven't >> heard any complaints >> but maybe others have been silent on this. I am not surprised at all >> that this happens. >> >> Aluminum chassis has the problem that it is a good conductor so when the >> whole enclosure forms >> around the cables, the aluminum can act as a shorted turn in a >> transformer. It is usually just >> lossy but should vibrate much less, if at all. >> >> There are other issues in switching to aluminum that Robin mentions, here: >> >> *"One reason is cost, the other is fasteners, We would need to use press >> nuts instead of snail shells. * >> *Snail shells and sheet metal screws don’t do well in aluminum. It is too >> soft. Aluminum would not * >> >> >> *vibrate from magnetic ripple activity though." *He has some ideas to >> make aluminum work so we will try those. >> >> Now, plastic could work. Just has to be real thick. Darn physics ! >> >> Damping can help, like Kirk tried (more can be done here too). Keeping >> the cables >> together best as you can inside the chassis may help as well but moving >> and routing >> the cables might also reduce the buzzing some more. >> >> That's the latest buzz from here. >> >> 🌜boB🌛 >> K7IQ >> >> On 6/30/2023 8:45 AM, david quattro via RE-wrenches wrote: >> >> Ferrite cores can be used for the battery cables to pass through to >> reduce common mode current >> >> On Fri, Jun 30, 2023 at 3:59 AM Kirk Herander via RE-wrenches < >> re-wrenches@lists.re-wrenches.org> wrote: >> >>> I have -15- sets of 4/0 cable (1 per 32 kwh stack) into the combiner. >>> They are paired and within .25 " of one another in wire cable tray for 80% >>> of their respective distance. >>> >>> The inverter to combiner sets are 2/0 for each respective inverter. They >>> are paired (not twisted) in cable tray, anywhere from 10 -20' in length. >>> Maybe I can send some photos, but can't at present due to computer issues. >>> >>> I used cable tray because the CT-rated cable is in free air, no derating >>> of current required. But merely pairing the leads may be the issue. >>> >>> I could rearrange the inverter cables and twist the sets, but doing it >>> from combiner to battery cabinets is impossible. >>> >>> And I'm wondering if this is really necessary if the customer is willing >>> to live with the issue. What are the ramifications down the road? >>> Loosening of connections I suppose would be one. >>> >>> >>> >>> On Fri, Jun 30, 2023 at 12:40 AM Jerry Shafer via RE-wrenches < >>> re-wrenches@lists.re-wrenches.org> wrote: >>> >>>> Kirk >>>> As the batteries come up to charge does the vibration subside. Are the >>>> battery cables spun together "corkscrew like" l have seen this correct DC >>>> noise. I have an 8 on 8 just like your 10 and l have no noise at all, mine >>>> come in from each side of the battery combiner, how is your install >>>> configured, how is the cable length same close or very short to very long >>>> some length is better on FLA's due to resistance under load and charge. >>>> More information may help with a solution. >>>> Fun times solar >>>> NABCEP PV Inspector >>>> >>>> On Thu, Jun 29, 2023, 8:19 AM Kirk Herander via RE-wrenches < >>>> re-wrenches@lists.re-wrenches.org> wrote: >>>> >>>>> All, >>>>> >>>>> I am in the middle of commissioning a 480kwh BP LFP battery bank, >>>>> connected to -10- OB Radian 8kw inverter/chargers. >>>>> >>>>> For the DC combiner I am using midnite 2000 amp combiner boxes, >>>>> modified to mount class T fuses on the positive bus, for both battery >>>>> inputs and inverter outputs. >>>>> >>>>> For starters, I set the master inverter at a max charge rate of 20 AC >>>>> amps, which equates to a DC charge of about 74 A. All the other inverters >>>>> are automatically set to this charge rate as well. >>>>> >>>>> Turning the chargers on one by one, I started to get quite an audible >>>>> vibration from the combiner box at a combined charge of about 400 to 500 >>>>> A. >>>>> >>>>> So I took the cover off of the combiner, which was vibrating >>>>> noticabllly by feel. Most of the noise was from the cover not fitting >>>>> tight. But the The box itself is also vibrating by feel. >>>>> >>>>> I took the combined charge up to 640A dc. This level of vibration >>>>> definitely increases with an increased charge rate. And I am surprised >>>>> because after all, we’re not talking AC here we’re talking DC. It almost >>>>> reminds me of a large AC transformer in its behavior. The vibration did >>>>> not >>>>> seem to be originating at the inverters, then resonating to the combiner. >>>>> >>>>> I can dampen the vibration by adding a few things, but I’m surprised >>>>> that this is happening. All connections in the combiner are tightened >>>>> properly. Ideas? >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> -- >>>>> >>>>> *Kirk Herander / **kirkh@vermont.solar <kirkh@vermont.solar>* >>>>> >>>>> *Owner|Principal, VT Solar, LLC* >>>>> >>>>> *Celebrating our 32st Anniversary 1991-2023!!* >>>>> >>>>> dba Vermont Solar Engineering >>>>> >>>>> 802.863.1202 >>>>> _______________________________________________ >>>>> List sponsored by Redwood Alliance >>>>> >>>>> Pay optional member dues here: http://re-wrenches.org >>>>> >>>>> List Address: RE-wrenches@lists.re-wrenches.org >>>>> >>>>> Change listserver email address & settings: >>>>> http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org >>>>> >>>>> There are two list archives for searching. When one doesn't work, try >>>>> the other: >>>>> https://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/ >>>>> http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org >>>>> >>>>> List rules & etiquette: >>>>> http://www.re-wrenches.org/etiquette.htm >>>>> >>>>> Check out or update participant bios: >>>>> http://www.members.re-wrenches.org >>>>> >>>>> _______________________________________________ >>>> List sponsored by Redwood Alliance >>>> >>>> Pay optional member dues here: http://re-wrenches.org >>>> >>>> List Address: RE-wrenches@lists.re-wrenches.org >>>> >>>> Change listserver email address & settings: >>>> http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org >>>> >>>> There are two list archives for searching. When one doesn't work, try >>>> the other: >>>> https://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/ >>>> http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org >>>> >>>> List rules & etiquette: >>>> http://www.re-wrenches.org/etiquette.htm >>>> >>>> Check out or update participant bios: >>>> http://www.members.re-wrenches.org >>>> >>>> >>> >>> -- >>> >>> *Kirk Herander / **kirkh@vermont.solar <kirkh@vermont.solar>* >>> >>> *Owner|Principal, VT Solar, LLC* >>> >>> *Celebrating our 32st Anniversary 1991-2023!!* >>> >>> dba Vermont Solar Engineering >>> >>> 802.863.1202 >>> _______________________________________________ >>> List sponsored by Redwood Alliance >>> >>> Pay optional member dues here: http://re-wrenches.org >>> >>> List Address: RE-wrenches@lists.re-wrenches.org >>> >>> Change listserver email address & settings: >>> http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org >>> >>> There are two list archives for searching. When one doesn't work, try >>> the other: >>> https://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/ >>> http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org >>> >>> List rules & etiquette: >>> http://www.re-wrenches.org/etiquette.htm >>> >>> Check out or update participant bios: >>> http://www.members.re-wrenches.org >>> >>> >> _______________________________________________ >> List sponsored by Redwood Alliance >> >> Pay optional member dues here: http://re-wrenches.org >> >> List Address: RE-wrenches@lists.re-wrenches.org >> >> Change listserver email address & >> settings:http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org >> >> There are two list archives for searching. When one doesn't work, try the >> other:https://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org >> >> List rules & etiquette:http://www.re-wrenches.org/etiquette.htm >> >> Check out or update participant bios:http://www.members.re-wrenches.org >> >> >> _______________________________________________ >> List sponsored by Redwood Alliance >> >> Pay optional member dues here: http://re-wrenches.org >> >> List Address: RE-wrenches@lists.re-wrenches.org >> >> Change listserver email address & settings: >> http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org >> >> There are two list archives for searching. When one doesn't work, try the >> other: >> https://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/ >> http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org >> >> List rules & etiquette: >> http://www.re-wrenches.org/etiquette.htm >> >> Check out or update participant bios: >> http://www.members.re-wrenches.org >> >> > > -- > > *Kirk Herander / **kirkh@vermont.solar <kirkh@vermont.solar>* > > *Owner|Principal, VT Solar, LLC* > > *Celebrating our 32st Anniversary 1991-2023!!* > > dba Vermont Solar Engineering > > 802.863.1202 > _______________________________________________ > List sponsored by Redwood Alliance > > Pay optional member dues here: http://re-wrenches.org > > List Address: RE-wrenches@lists.re-wrenches.org > > Change listserver email address & settings: > http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org > > There are two list archives for searching. When one doesn't work, try the > other: > https://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/ > http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org > > List rules & etiquette: > http://www.re-wrenches.org/etiquette.htm > > Check out or update participant bios: > http://www.members.re-wrenches.org > >
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