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UPS Whine/Buzz/Squeal when Water Heater is turned ON

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I have designed cascaded SMPS before where the switched load created a condition called chaos where the switcher coil sounded like a speaker coil of running water. It was epoxied but still produced audio. Added a low ESR on the DC input supplied from another SMPS like your PC PSU and the switchers on the motherboard making your PSU sound bad. It is just a bad combination of modes that creates an instability than creates resonance or in my case amplified white noise. Load factors were within spec.

But in this case the inverter has insufficient load to regulate the current and has low duty cycle spurious noise in the audio range, instead of above the audio range.

---------- Post added at 03:34 ---------- Previous post was at 03:31 ----------

acoustic noises in coils are usually due to micro motions from high magnetic forces and lack of rigid encapsolation or air entrapment. Cant say as I have test many though

Video GPU power swings I am not familiar, what does it sound like? video vertical sweep rate or content modulation?

Of course acoustic noise is not a sure indicator that Electrical conducted ripple is bad.
 
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I tried giving the UPS a 153W (17% of its total capacity) load and the buzzing sound is still there. What next?

And by the way, the sound is also audible even when the UPS is OFF as long as it is plugged in the AC socket.
 

Does it sound like a tungten edison bulb with a dimmer on minimum?


Your UPS has common mode coils on line & neutral to the AC input. Take a plastic hose to listen where the sound comes from.

Once the problem is understood, the solution is obvious.

... Otherwise, what is the point?
 

SunnySkyguy said:
Does it sound like a tungten edison bulb with a dimmer on minimum?


Your UPS has common mode coils on line & neutral to the AC input. Take a plastic hose to listen where the sound comes from.

Once the problem is understood, the solution is obvious.

... Otherwise, what is the point?
Click to expand...

I don't know how that sounds.

So you're saying that the noise is normal for the UPS?
 

The conventional 60 or 100W bulb ( a.k.a. Edison bulb) has a coiled tungsten filament. When it is operated from a wall dimmer switch using a triac. the surge currents are high at firing, When Dim, the average power is 10% but the current spikes from being cool may be 5x normal peak current. When this repeats at a 60 or 120 Hz rate or 50/100Hz it makes the sound like a faint pinging spring at that rate due to the forces not being sinusoidal but rather pulsed from a fast rising edge.

Ref: **broken link removed** If you see the common mode choke coil suggest for this dimmer, you should find your UPS already has one. Possibly it has a resonance with a harmonic of the line frequency.

What I dont understand is why your water heater would trigger this resonance, as it should have fairly linear sinusoidal current from a linear resistance and stead AC voltage.

Anyways, I can only make wild guesses without some test results to isolate the waveform and sound. Good luck.
 

SunnySkyguy said:
What I dont understand is why your water heater would trigger this resonance, as it should have fairly linear sinusoidal current from a linear resistance and stead AC voltage.
Click to expand...

I still say it's due to the voltage drop from the extra load on the mains wiring.
 

FoxyRick said:
I still say it's due to the voltage drop from the extra load on the mains wiring.
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Well, I don't see any voltage drop in the display of my UPS? And the AVR of my UPS isn't working (I already tried setting it to the lowest sensitvity).
 

Sounds like very high shape factor periodic loads in the audio band.

Can you scope the input waveform for power with/without noise? RMS value might not change but spikes might be significant.
 
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I think they have problem with filtering of input AC. Maybe they skip some parts to make device cheaper.
 

kevindd992002 said:
So with that I don't have any choice?
Click to expand...

Choices depends from several things. If You are in some nice country You can return device and say that you not satisfied with this and whant other device. Try to documents with video your problem and send them link on youtube.

Try to check your mains voltage, with and without heater. Try with other heavy loads. Measure voltage with loads. Check grounding in house/object.
 

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