[RE-wrenches] X-240 Buzz

[Alex MeVay]

One thing you might want to check is for any DC getting into the
transformer.  This can cause the transformer to saturate on one side
of the sinewave, leading to high peak currents and a buzz.  You can
try checking for this by putting a DMM set to DC across the AC line.
Should be well under a volt.  Be sure to use a quality DMM, as cheaper
ones might not be able to fully reject the AC, and some of it might
show up as a DC reading.  To make sure the meter isn't playing tricks
on you, you can also try reversing the meter polarity and making sure
the DC reading inverts too.

Admittedly, I haven't encountered this with an inverter before, just
at a friend's apartment, where the DC caused an immediate breaker trip
when a large 120->240 transformer was connected.  I can sort of
imagine a situation where an inverter that's not quite working quite
right has a little DC offset at light loads, but that this goes away
at heavier loads.

Let us know what you find,

Alex MeVay

Genasun * Blue Sky Energy * http://sunforgellc.com

On Mon, Jan 31, 2022 at 7:51 AM Foxfire Energy <dan at foxfire-energy.com> wrote:
>
> Not positive, but I’d suspect resonant frequencies.. might be simple as using flat washers under the mounting screws.. maybe try adding an inductive load to skew the power factor.. gobs of information online.. good luck. db
>
> Sent from my iPhone
>
> > On Jan 31, 2022, at 10:34 AM, drake.chamberlin at redwoodalliance.org wrote:
> >
> > 
> > An Outback X-240 auto transformer on a VFX3648 buzzes loudly with a load of 400 W. The sound diminishes and finally stops with higher loads.
> >
> > The load was an electric, oil filled space heater.
> >
> > Has anyone seen this before?
> >
> > Thank you,
> >
> > Drake
> >
> > Drake Chamberlin
> > Athens Electric LLC
> > Ohio Electrical Contractor’s License 44810
> > CO Master Electrician’s License 4526
> > NABCEP Certified PV Installation Professional
> >
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