<html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class="">You may already know but… Are your DC cables bonded together and twisted where possible to reduce magnetic fields? Higher the current and greater the loop area, the stronger the fields are. More parallel loops, the greater the combined flux = loud Hums. <div class=""><div style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); font-family: Helvetica; font-size: 14px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; text-decoration: none;"><br class=""></div><div style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); font-family: Helvetica; font-size: 14px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; text-decoration: none;">Larry Crutcher</div><div style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); font-family: Helvetica; font-size: 14px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; text-decoration: none;">Starlight Solar Power Systems</div><div style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); font-family: Helvetica; font-size: 14px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; text-decoration: none;"><br class=""></div><div style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); font-family: Helvetica; font-size: 14px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; text-decoration: none;" class=""><br class=""></div><br class="Apple-interchange-newline">
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<div><br class=""><div class="">On Jun 29, 2023, at 8:19 AM, Kirk Herander via RE-wrenches <<a href="mailto:re-wrenches@lists.re-wrenches.org" class="">re-wrenches@lists.re-wrenches.org</a>> wrote:</div><br class="Apple-interchange-newline"><div class="">All, <div dir="auto" class=""><br class=""></div><div dir="auto" class="">I am in the middle of commissioning a 480kwh BP LFP battery bank, connected to -10- OB Radian 8kw inverter/chargers.</div><div dir="auto" class=""><br class=""></div><div dir="auto" class="">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.</div><div dir="auto" class=""><br class=""></div><div dir="auto" class="">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.</div><div dir="auto" class=""><br class=""></div><div dir="auto" class="">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. </div><div dir="auto" class=""><br class=""></div><div dir="auto" class="">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.</div><div dir="auto" class=""><br class=""></div><div dir="auto" class="">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.</div><div dir="auto" class=""><br class=""></div><div dir="auto" class="">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?</div><div dir="auto" class=""><br class=""></div><div dir="auto" class=""><br class=""></div><div dir="auto" class=""><br class=""></div><div dir="auto" class=""><br class=""></div><div dir="auto" class=""><br class=""></div><div dir="auto" class=""><br class=""></div><div dir="auto" class=""><br class=""></div><div dir="auto" class=""><br class=""></div><div dir="auto" class=""><br class=""></div><div dir="auto" class=""><br class=""></div><span class="gmail_signature_prefix">-- </span><br class=""><div dir="ltr" class="gmail_signature" data-smartmail="gmail_signature"><div dir="ltr" class=""><div style="font-family: Arial; font-size: 16px; margin: 0in 0in 0.0001pt;" class=""><span style="font-size:10pt" class=""><a name="SignatureSanitizer__MailAutoSig" class=""><b class="">Kirk Herander / </b></a><b class=""><a href="mailto:kirkh@vermont.solar" title="Send an email to kirkh@vermont.solar; Send an email to kirkh@vermont.solar" style="color:blue" target="_blank" class="">kirkh@vermont.solar</a></b></span></div><div style="font-family: Arial; font-size: 16px; margin: 0in 0in 0.0001pt;" class=""><span style="font-size:10pt" class=""><b class="">Owner|Principal, VT Solar, LLC</b></span></div><div style="font-family: Arial; font-size: 16px; margin: 0in 0in 0.0001pt;" class=""><span style="font-size:10pt" class=""><b class=""><i class="">Celebrating our 32<sup class="">st</sup> Anniversary 1991-2023!!</i></b></span></div><div style="font-family: Arial; font-size: 16px; margin: 0in 0in 0.0001pt;" class=""><span style="font-size:10pt" class="">dba Vermont Solar Engineering</span><br class=""></div><div style="font-family: Arial; font-size: 16px; margin: 0in 0in 0.0001pt;" class=""><span style="font-size:10pt" class="">802.863.1202</span></div></div></div>
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