In my experience, adding large electrolytic filter caps at the inverter seems to help quite a bit with ac ripple issues and increases inverter efficiency a bit as well.
Roy Rakobitsch NABCEP Certified Small Wind Installer® NABCEP Certified Solar PV Installer® Certified Advanced Tower Climbing, Safety & Rescue Wind/PV Design Engineer Windsine LLC 631-514-4166 www.windsine.org On Jun 29, 2015 5:05 PM, "Ray Walters" <r...@solarray.com> wrote: > This is fascinating because while I knew the DC cables had an AC > component, I never realized how much inductance played in the volt drop to > the inverter. Thanks for bringing this to our attention Jarmo. > Which brings up another question based on Benn's question: isn't the > battery itself part of the inductive loop? and would the lead inside and > steel cases act to increase the inductance? Should we consider changing > battery layouts not just to shorten cable lengths, but to counter > inductance in the batteries themselves? If needed, we could actually wire > the batteries to "twist" by putting every other 2 v cell in the opposite > row. > My guess is that it wouldn't be worth it, but I've been wrong many > times....... > > R.Ray Walters > CTO, Solarray, Inc > Nabcep Certified PV Installer, > Licensed Master Electrician > Solar Design Engineer303 505-8760 > > On 6/29/2015 3:55 PM, Benn Kilburn wrote: > > What about when you have the (+) and (-) terminals at opposite ends of a > larger battery bank? Sure you can run the conductors side-by-side once > they meet up on their way to the inverter, but would you consider the > distance between the end terminals a "large loop"? > Ideally the battery string is laid out so the end terminals are close > together and close to the inverter, but this isn't always the case. > > Benn Kilburn > SkyFire Energy Inc. > 780-906-7807 > > > On Jun 29, 2015, at 10:28 AM, jarmo.venalai...@schneider-electric.com > wrote: > > Hi: > > From the comments so far, it appears that within the wrenches group, good > practices are the rule and DC cables are kept side by side, so the problem > I mentioned hasn't come up much. > > I have seen "large loop" battery cables a couple of times in solar > installs myself out on islands way down south. Also on boats/RV's/motor > homes. > > Please keep the cable loop in mind when you do bench tests of inverters, > as it may screw up the results and make it seem like there is something > wrong with the inverter. > > JARMO > > _____________________________________________________________________________________ > > * Jarmo Venalainen* | * Schneider Electric ** | Xantrex Brand* | > *CANADA* | *Sales Application Engineer* > * Phone:* +604-422-2528 | *Tech Support:* 800-670-0707 | *Mobile:* > +604-505-0291 > * Email:* *jarmo.venalai...@schneider-electric.com* > <jarmo.venalai...@schneider-electric.com> | *Site:** www.Xantrex.com* > <http://www.xantrex.com/> | *Address:* 3700 Gilmore Way, Burnaby, BC > V5G4M1 > <mime-attachment.gif> <http://www.xantrexrebate.com/> > <mime-attachment.gif> <http://www.xantrex.com/> <mime-attachment.gif> > <https://www.facebook.com/Xantrex> <mime-attachment.gif> > <https://twitter.com/Xantrex> <mime-attachment.gif> > <https://twitter.com/Xantrex> > > > *** Please consider the environment before printing this e-mail > > > > From: "b...@midnitesolar.com" <b...@midnitesolar.com> To: RE-wrenches < > re-wrenches@lists.re-wrenches.org>, Date: 06/28/2015 10:30 PM Subject: Re: > [RE-wrenches] Battery Bank to Inverter Wiring Sent by: "RE-wrenches" < > re-wrenches-boun...@lists.re-wrenches.org> > ------------------------------ > > > > > On 6/28/2015 9:20 AM, Allan Sindelar wrote: > >>>>I'm not an EE, but I can't see what difference twisting would make in > the absence of a building/collapsing field as is normal with AC.<<<< > > It is little known that with the typical inverters that use the heavy > power transformers, > have a lot of AC 120 Hz (or 100 Hz for 50 Hz systems) current mixed in > with that DC battery current. > > The AC output current reflects back to the input as ripple current. This > is why you want to > have at least short as possible Sbattery cable runs AND keep the wires as > close together as possible. > > Twisting the battery cables may help a bit but that is probably overkill. > > The problem has to do with inductance in the battery cables. You can use > as big of cable > as you can fit in to reduce resistance, but that will not help to lower > the inductance. > The problems you can sometimes have with high inductance is that L-C > resonance at the > inverter can raise the peak voltages seen at the inverter input terminals > and can be hard on > the inverter. > > Then again, the high frequency, lighter weight inverters will typically > keep most of that ripple > inside, between the DC input and AC output and battery cable inductance > will not be as much > of a problem on the battery cables. > > boB Gudgel > > > > > On 6/28/2015 9:20 AM, Allan Sindelar wrote: > As a matter of course I have always run the positive and negative > conductors of high-current cable pairs together, but have never > deliberately twisted them, and have never known of any related problems. > The most obvious example of this would be 4/0 battery/inverter cables in a > 24V system, with a 250A GJ-class breaker or (prior to that) a 300A or 400A > Class T fuse. It's pretty tough to thread a twisted pair of 4/0 USE/RHH/RHW > cables through a 2" elbow or LB from inverter enclosure to battery > enclosure. > I'm not an EE, but I can't see what difference twisting would make in the > absence of a building/collapsing field as is normal with AC. > I have twisted AC conductors together in the past when clients have > expressed concerns about EMF from their equipment and wiring, but only AC. > Allan > > *Allan Sindelar* > *al...@sindelarsolar.com* <al...@sindelarsolar.com> > NABCEP Certified PV Installation Professional > NABCEP Certified Technical Sales Professional > New Mexico EE98J Journeyman Electrician > Founder (Retired), Positive Energy, Inc. > * 505 780-2738 <505%20780-2738> cell* > > > > On 6/27/2015 2:40 AM, John wrote: > That is why for years we have been twisting those leads around each > other. I was told it was to cancel out the opposing fields on the wires, > but for whatever the correct technical reason is, we have always twisted > those heavy wires. John V. > > *From:* RE-wrenches [*mailto:re-wrenches-boun...@lists.re-wrenches.org* > <re-wrenches-boun...@lists.re-wrenches.org>] *On Behalf Of * > *jarmo.venalai...@schneider-electric.com* > <jarmo.venalai...@schneider-electric.com> > * Sent:* Saturday, 27 June 2015 5:45 a.m. > * To:* RE-wrenches > * Subject:* [RE-wrenches] Battery Bank to Inverter Wiring > > Hi: > > From time to time over the years I've come across systems where the > routing of DC cables between the batteries and the inverter has been the > cause of issues. > > I'm not referring to wire thickness or quality of terminations. For the > purposes of this discussion, just assume that wire thickness and > terminations are perfect. > > What I am referring to is the routing of the positive and negative battery > cables. In particular, the loop area within the + and - cables as shown in > the image below, > > The problem I've seen in systems with a large loop in the setup is that > the inverter does not provide good surge power and can even go into low > voltage shutdown during large surges. > > Recently this happened again and I wanted to get a better feel for it, so > I did some math. > > For a cable length of about 12', the loop is an inductor which has a value > of inductance of about 1 uH for side by side cables and as much as 6 uH for > cables about 1 foot apart. > > This inductance is greatly multiplied by any ferrous metal in the loop and > can easily be in the range of 10's to 100's of uH. Examples being cables > which run in steel conduits or along the steel frame of a motor home. > > Inductance causes a voltage drop proportional to the rate at which the > current is changing. To get an idea of how large that rate can be for > typical inverters, I did surge tests with a 5kW inverter and found that the > rate of change of current can be as high as 100A per milli-second or > 100,000 Amps/second. > > Given that, the voltage drop of the wire inductance is then , Vdrop = > (rate of change of current) x (inductance), > > Vdrop for 1 uH = (100,000 A/s) x (0.000001 H) = 0.1V > Vdrop for 10 uH = (100,000 A/s) x (0.000001 H) = 1.0V > Vdrop for 100 uH = (100,000 A/s) x (0.000001 H) = 10.0V clearly this is > a problem. > > Have any of the wrenches had systems with this issue? If so, how often. > > > JARMO > > > > > ______________________________________________________________________ > This email has been scanned by the Symantec Email Security.cloud service. > ______________________________________________________________________ > _______________________________________________ > List sponsored by Redwood Alliance > > 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 > > List-Archive: > http://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/maillist.html > > List rules & etiquette: > www.re-wrenches.org/etiquette.htm > > Check out or update participant bios: > www.members.re-wrenches.org > > > > _______________________________________________ > List sponsored by Redwood Alliance > > 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 > > List-Archive: > http://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/maillist.html > > List rules & etiquette: > www.re-wrenches.org/etiquette.htm > > Check out or update participant bios: > www.members.re-wrenches.org > > > > _______________________________________________ > List sponsored by Redwood Alliance > > 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 > > List-Archive: > http://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/maillist.html > > List rules & etiquette:www.re-wrenches.org/etiquette.htm > > Check out or update participant bios:www.members.re-wrenches.org > > > > _______________________________________________ > List sponsored by Redwood Alliance > > 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 > > List-Archive: > http://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/maillist.html > > List rules & etiquette: > www.re-wrenches.org/etiquette.htm > > Check out or update participant bios: > www.members.re-wrenches.org > > >
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