WS-24-400B PSU's electrical buzz when UPS battery powered

[bayamon]

Hi,

My WS-24-400B Rev D makes a loud electrical buzz from the PSU when powered from battery backup UPS.

It happen with a APC Backups pro 1500 and with a TRV NEO 500 (this I think is a rebranded Powercom UPS). With the APC is more loudly than with the rebranded Powercom.

Both UPS are stepped sine wave and rated 230V 50hz, they work fine with other electronic equipment and only makes a buzz in netonix PSU.

I've tested with the netonix powering 10 poes (70W aprox) and with the netonix idling with no poe, same buzz. No other equipments to the UPS.

The netonix start the fan noticeable more often while battery powered than with electric grid power, so maybe it is heating more.

[mike99]

Does the switch make a buzz plug directly in a power outlet without UPS ?

We use Cyberpower UPS and never had problems like this. Maybe the PSU of the switch is defect.

[bayamon]

The PSU does not make a buzz with the electric grid.

Pinged Some other WISP in my area with similar UPS and at least 2 of them are reporting the same buzz with APC and lyonn UPS with stepped sine wave, only when battery powered. Other WISP with pure sine wave UPS report no buzz at all.

I think this is a stepped sine wave issue with the PSU. And possibly only with 230V 50hz input.

Are you using a stepped sine wave UPS? It is 110V or 230V, 50, 60hz?

[sirhc]

I thought I answered this for you?

Your power supply is not providing sufficient current or dirty power.

Get a new UPS.

[bayamon]

No, you don't talked to me. But I reported this on other forum and someone conacted you about this.

The UPS is not overloaded, buzz happens ever with the netonix idling and nothing more connected to the UPS.

To me it happend with two different UPS, with other reporting the same with even other brands of UPS, all stepped sine wave.

Maybe is "dirty power" from the UPS, but why is only netonix buzzing and no other equipment with same UPS?

[bayamon]

Try a APC backups pro 1500va with 230v output to a netonix.

[sirhc]

I do not know but obviously the power supply does not like the power from the UPS?

My guess would be the Hz.

Our power supply is rated for both 50 and 60 Hz.

Could be the wave form as well?

But if you plug it into the grid it works fine which the power companies are most time very accurate on the Hz and the wave is clean.

Also possibly the UPS does not have access to a good earth ground to pass to the switch?

[bayamon]

All the UPS that make a buzz have in common that output a stepped sine wave form instead of a pure wave form (as in the electrical grid).

Maybe is something that only happen at 230V 50hz. I dont know

But the buzz and the fact that the fans start more often may be indicating an over heating of the PSU.

I dont have the knowledge for assuming this is a bad thing and may short the life of the PSU, but I think is worth investigating and if there is a problem make a revision on the design.

UPS with stepped sine wave are ubiquitious here and this is the first electronic I encounter with a problem with it.

[sirhc]

We do not design and build our AC power supplies, it was designed and built by a company that all they do is designs and build AC power supplies.

The company is the same company that designs and builds power supplies for Ubiquiti as well.

This power supply was not a special design for us, we pulled it from a common one that they build hundreds of thousands of per year for many other purposes and this unit design is several years old so I do not think there is a design flaw in it?

We designed and build our SMART DC power supplies because they are one of a kind special but we purchase our AC powers supplies because the cost to design and get AC power supplies certified is extremely slow and expensive process because of all the differnt country regulations and certifications.