[RE-wrenches] High current dc combiner vibration

[Kirk Herander]

I have not twisted them. It is a lot of Cable as you might imagine and they
aren’t paired close together individual inverter to combiner or combiner to
battery cabinets, not 100% of the cable lengths anyway, maybe on average
80%

On Thu, Jun 29, 2023 at 12:25 PM Starlight <larry at starlightsolar.com> wrote:

> 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.
>
> Larry Crutcher
> Starlight Solar Power Systems
>
>
>
>
> On Jun 29, 2023, at 8:19 AM, Kirk Herander via RE-wrenches <
> re-wrenches at 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 at vermont.solar <kirkh at vermont.solar>*
> *Owner|Principal, VT Solar, LLC*
> *Celebrating our 32st Anniversary 1991-2023!!*
> dba Vermont Solar Engineering
> 802.863.1202
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> --

*Kirk Herander / **kirkh at vermont.solar <kirkh at vermont.solar>*

*Owner|Principal, VT Solar, LLC*

*Celebrating our 32st Anniversary 1991-2023!!*

dba Vermont Solar Engineering

802.863.1202
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