Hi all,

I've just installed a Multiplus II 48/3000 in my kitchen and while it works as advertised, the transformer hum is pretty loud. The inverter is silent when inverting, I've also verified that it's not the charger responsible for this hum. There are reports online of others suffering from this but I have yet to find a solution, I'm wondering if anyone here may have found a workaround before I relocate this inverter to the garage.

Thanks

Edited June 4, 20233 yr by Cumulus

Hi, 

The hum that you hear is quite normal. Because the Victron is a low frequency inverter, it will generate a hum. (Similar to the Hum you would hear at free standing transformers in your neighbourhood. 
 

Mine is doing exactly the same.  I call it, the Sound of Power! 

13 hours ago, Cumulus said:

The inverter is silent when inverting,

Well, then when does it make the noise?  Only at power pass-through?

The Multiplus-I uses two toroidal transformers and the Multiplus-II apparently only one.  The transformer is used as the voltage step-up device in these so-called low frequency inverters.  I think it is also used as a step-down transformer for battery charging.  If it is silent during inverting, it means that it is not the transformer, but some other choke or inductor.  Possibly the mains input filter that will be a rather large common-mode inductor.

I am not sure how Victron mounts these massively heavy transformers.  Smaller Toroidal transformers are normally clamped between two metal disks with large rubber washers.  Tightening the single bolt through the centre would tighten the rubber clamp and could reduce the resonance.   However, toroidal transformers have many layers of isolation tape between the various windings and the outer winding is also taped shut.   So it is unlikely to be the transformer.

Noise, be it low frequency hum or high frequency noise, is always generated by magnetic components - chokes, inductors and transformers.  Irrespective of inverter type and manufacturer, I have seen a lot of bare enamel copper wire without any coating.  These components should at least be bound with tape or some form of silicon, rubber, glue, epoxy or lacquer to prevent the windings from vibrating.  One could use neutral curing silicon on these components, but this would not go down well if the inverter has a problem and needs to go back to the agent for under-warranty repair.

It is very disappointing to hear that the expensive Mercedes of inverters, is allowed to pass QA and be vocal once it is asked to perform it's duty....

Even very small power devices can sometimes make a racket.  I have a bathroom LED fitting that sometimes causes a rather loud buzz on the thin gauge metal base plate.  It's not always the large, high power components.

55 minutes ago, Modina said:

It is very disappointing to hear that the expensive Mercedes of inverters, is allowed to pass QA and be vocal once it is asked to perform it's duty....

It's called a Monday or is it a Friday Machine. 🤔

Still, not funny when it's your machine.

See if you can find another Multiplus II 48/3000 nearby, and ask if you can "listen" to their machine and compare.

If theirs is quiet, ask for a replacement?

I have a Multiplus-II so far it is is pretty silent. It seems to make the loudest humming noise when connecting loads that typically generate harmonic's. Eg: The most noticeable is a hair dryer used at half its power setting (clipped sine wave). This is during normal and inverter operation.  Perhaps you could try isolate each of your loads in turn and see if the hum improves. This would rule out the possibility of load causing the hum.

Thank you for all the input to this problem - I'm obviously bitterly disappointed and now just leave the inverter switched off and bypassed entirely until I need it for loadshedding - which is pretty unsatisfactory. 

The hum present regardless of loads or charging - I've disconnected the output from the inverter and switched off the charger function to confirm this and its completely silent when inverting and the mains is switched off. 

I wonder if there's something about my installation causing the transformer to hum? 

It sounds very similar to the buzzing heard in this short clip prior to him cranking up the load which gets the fans running. 

 

Edited June 6, 20233 yr by Cumulus