Inverter causing line noise?

[dark_ride]

Hi Everyone,

So I've been using my inverter a couple months and noticed that when I'm running the small space heater under my desk that I get a whining noise from my powered speakers, which are being powered by grid power as is basically everything else on my desk. It's a wzrelb 3000w 24v pure sine wave inverter. Out of curiosity I set the 3.5mm plug from the speakers next to the extension cord I'm using and of course it got much worse. If I plug the extension cord into gird power, then there's no noise at all. Upon further investigation, the noise is suspiciously similar to the 60hz square wave samples I came across. Is it safe to assume this inverter is defective or is this something normal?

I unfortunately don't have an oscilloscope to confirm its output. But if there's another test to try I'm willing to do some more diagnosis. I did plug in a fan just to see but it didn't seem to make extra noise like i experienced with a cheap modified wave inverter.

Thanks!

 

[v_green57]

"Pure sine wave" inverters are, well, not pure sine wave. Sometimes up to 10% distortion on cheap brands. The distortion is sometimes a high frequency that generates hash.

You can try playing with ferrites on the 24V leads to see if you can snub the hash down.

The reason you get the interference with the heater and not the fan is that the heater is a much larger load.

 

[dark_ride]

I get the interference noise with and without load. You think I should try ferrites on the input side of the inverter and not the output? I did confirm that even if I isolate the inverter from the solar and just use battery power that it still does it. I have 2/0 cable feeding the inverter.

I intend to start using it to power appliances, so I want to make sure it's not going to damage them long term.

 

[v_green57]

I get the interference noise with and without load. You think I should try ferrites on the input side of the inverter and not the output? I did confirm that even if I isolate the inverter from the solar and just use battery power that it still does it. I have 2/0 cable feeding the inverter.

I intend to start using it to power appliances, so I want to make sure it's not going to damage them long term.

You can try them on both sides. No harm, no foul.

Do you have any kind of steel box you could temporarily put the inverter in - create a Faraday cage? Might not be good long term, due to heating issues, but would narrow things down to the garbage being radiated by the inverter itself, the cabling, or both.

 

[dark_ride]

You can try them on both sides. No harm, no foul.

Do you have any kind of steel box you could temporarily put the inverter in - create a Faraday cage? Might not be good long term, due to heating issues, but would narrow things down to the garbage being radiated by the inverter itself, the cabling, or both.

I should be able to find something. I'll give that a shot and see if anything changes.

 

[AlpineJoe]

Try a different wall wart for your speakers.

As the others wrote, PSW may not be pure. Also the switching side of the electronics can cause EMI to be conducted to the AC side of the inverter.