What's actually causing my PSU to buzz/crackle when on UPS battery power?

[Parthu1708]

This is an addendum to another question I've had (which is now solved)...

The PC I just built has a Corsair HX1000i PSU and it doesn't like being fed the 'step-approximated sine wave' outputted by my Back-UPS BR1500G-IN. There's a constant crackling/buzzing coming from the PSU whenever the UPS goes on battery mode. The Corsair support rep advised to get a Pure Sine wave UPS but also said that if the PSU only runs for a few minutes on my current UPS before I shut it down after an outage, the buzzing shouldn't be a big deal.

But a local UPS retailer is saying that the noise from PSU is because of the voltage drop when the UPS is on battery (the city's input is ~240v where I live, but when on battery the UPS drops it to about ~214v) and that I'll need an on-line double conversion UPS to make this problem go away.

But aren't these modern PSUs supposed to be able to handle voltages in any part of the world, which includes the likes of the US where the input is only ~120v? So how could the comparatively slight drop to ~214v be making the PSU work so hard? Is he wrong or do I really need an on-line UPS?

I was planning on buying a line-interactive pure sinewave UPS like the Smart-UPS SUA1500I-IND but now I'm confused if that will actually solve my problem or not.

[Teken · Accepted solution]

The noise you hear from the computer PSU is because it uses a PFC topology. The APC UPS the representative suggested is perfectly fine as it outputs a pure sine wave exactly like what comes out of the AC Mains outlet in your home.

A stepped approximate sine wave (PWM) UPS will cause the buzzing sound you hear. Despite popular belief this buzzing is NOT safe for the electronics! ☝️

One only needs to use common sense and (Think) what happens to something that used to make no sound?!? 🤔 Now does because it’s literally and physically vibrating!!! 🤦‍♂️👎

Lastly, the benefits of a On-Line double conversion UPS is the connected load is provided conditioned (Pure Sine Wave) voltage all the time. Meaning there is zero transfer time and thus output power (voltage) is always clean, protected, and highly regulated to the connected load. 👍

[Parthu1708]

Hi, I went ahead and purchased a Pure Sinewave UPS (APC Smart-UPS SUA1500I-IND) and I'm happy to announce that the buzzing noise issue when on battery has been resolved! Now my computer's PSU is silent regardless of whether it's running on the city's utility power or the UPS' battery power.

[Teken]

Great to hear - Rock On 🤘