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High-pitched, pulsating noise from Axpert


wolfandy
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Hi all

I am getting a high-pitched, pulsating noise when I am running my aircon(s) that are connected to my Axpert inverters. The noise is not present when the aircon(s) are switched off. The aircons are each on separate circuit breakers.

I can pick up the noise in 2 places:

  1. At the upper end of one of my Axpert inverters (the other one is dead silent)
  2. In any of my sound systems around the house (not only in a single location, so e.g. also in bedroom system if only office aircon is on)

Especially point 1 above makes me believe that the Axpert is the source. What do you guys think? Has anyone had something similar before?

@Coulomb: I am strongly hoping that with your infinite experience and wisdom you have come across something like this before and will have a solution 🙂

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10 hours ago, wolfandy said:

I am getting a high-pitched, pulsating noise when I am running my aircon(s) that are connected to my Axpert inverters.

So this is line a ping ping ping with each ping being high pitched (4 kHz or more?) and what... one second apart? One tenth of a second?

Quote

The noise is not present when the aircon(s) are switched off. 

So you're sure it doesn't happen with other high powered loads, e.g. kettle?

Quote

 

I can pick up the noise in 2 places:

  1. At the upper end of one of my Axpert inverters (the other one is dead silent.

 

So that's an acoustic sound, right?

Quote

2. In any of my sound systems around the house (not only in a single location, so e.g. also in bedroom system if only office aircon is on)

So you hear that in your speakers, but the signal must be coming from the inverter as either radio frequency, or a disturbance on the mains powering the sound systems.

Quote

Especially point 1 above makes me believe that the Axpert is the source. What do you guys think? Has anyone had something similar before?

What I have experienced before that is only vaguely suggestive of this is when certain loads (for me, especially my reflow soldering station (hot air gun), which causes lights to flicker. Do you notice lights flickering as well?

Quote

I am strongly hoping that with your infinite experience and wisdom ...

No pressure, then 🙂

Are your air conditioners the inverter type? I'm thinking that perhaps their switching frequency might happen to be close to that of the Axperts, and that's causing the voltage regulating system to get confused somehow. But I can't see why it would affect one Axpert and not the other. The switching frequencies would not be identical, but the timing is derived from crystal oscillators, so I'd expect them to be very close. I have a pair of old PF0.8 MKS models, and they seem to drive our one inverter based air conditioner just fine.

The only other thing that comes to mind is that perhaps the capacitors on one of them is starting to dry up. Is one Axpert older than the other? The pulsing reminds me of "motor boating" in radios, which is fixed by a good bypass capacitor. But I don't see why it would only manifest when the air conditioner(s) is(are) on.

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I've noticed on my Axpert King, it does not deal well with cheaply designed electronics.  Specifically ones that have very low power factor and rely on things like a TRIAC.

For example plugging in one of these super low budget hot air "stations" makes the lights pulse.  When I opened it, it was controlling the hot air gun with a TRIAC and basically nothing else in there.

I don't even think this is a problem unique to the Axpert, probably this will be an issue for any inverter.

If the AC relies on TRIAC to drive the fan (or god forbid the compressor) you are out of luck.  This would likely only be true on a really, really cheap air conditioner.  Alternatively a really low cost inverter AC could have the same problem if the power factor is atrocious.

Low pass filter (EMI filter) might remove this problem, worth a try maybe?

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Thanks for the feedback, @Coulomb and @Gnome

7 hours ago, Coulomb said:

So this is line a ping ping ping with each ping being high pitched (4 kHz or more?) and what... one second apart? One tenth of a second?

It's difficult to describe. I have uploaded videos of the noises (turn volume up 😉):

Speaker - https://streamable.com/gi3288

Inverter - https://streamable.com/nd9c97

7 hours ago, Coulomb said:

So you're sure it doesn't happen with other high powered loads, e.g. kettle?

No. 4kW of non-aircon loads (kettle, pool pump, vacuum, etc) does not produce the noise - but 1.8kW of aircon load does

18 hours ago, wolfandy said:

At the upper end of one of my Axpert inverters (the other one is dead silent)

Today I noticed that actually both inverters are producing the noise

7 hours ago, Coulomb said:

So that's an acoustic sound, right?

I don't really now how to describe it. Hope the videos above help

7 hours ago, Coulomb said:

Do you notice lights flickering as well?

No, I do not notice flickering in any of my LED lights anywhere in the house

7 hours ago, Coulomb said:

Are your air conditioners the inverter type?

Yes, both of them are

7 hours ago, Coulomb said:

I have a pair of old PF0.8 MKS models, and they seem to drive our one inverter based air conditioner just fine.

I also have old PF0.8 models

7 hours ago, Coulomb said:

Is one Axpert older than the other? The pulsing reminds me of "motor boating" in radios, which is fixed by a good bypass capacitor. But I don't see why it would only manifest when the air conditioner(s) is(are) on.

Both are similar in age (about 1 year apart). But please note my comment above that now it seems to come from both inverters

7 hours ago, Coulomb said:

The only other thing that comes to mind is that perhaps the capacitors on one of them is starting to dry up.

I cannot remember having had this problem in the past. The only thing that I had done was replace the caps with your recommendations from the AEVA forum. Could that have anything to do with it?

1 hour ago, Gnome said:

This would likely only be true on a really, really cheap air conditioner. 

Both aircons are mid-of-the-range Daikins, so I would hope not

1 hour ago, Gnome said:

Low pass filter (EMI filter) might remove this problem, worth a try maybe?

Do you know where to get something like this locally? At that price, I would be happy to give it a try

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Sorry to get back to this so late.

On 2021/01/13 at 9:36 PM, wolfandy said:

It's difficult to describe. I have uploaded videos of the noises (turn volume up 😉😞

Speaker - https://streamable.com/gi3288

Inverter - https://streamable.com/nd9c97

Those sounds remind me of packets of data. For example, like the sound you can hear in some audio gear when your mobile phone gets a call.

Do you perhaps have a WiFi or Bluetooth data sender connected to the inverters?

Of course, I can't think of a reason why they would be triggered only when the air conditioners are on. Unless the air conditioners are controlled by some digital packets? I assume that this doesn't correspond with someone in your family pressing buttons on their infra-red remote for their air conditioner.

Maybe the in-house unit (with the evaporator) talks to the grunt box (with the condenser and compressor) wirelessly? Or via power-line communications, that "sound out" in the inverter because there are inductors in there that may have some sort of magnetostriction happening?

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5 minutes ago, Coulomb said:

Sorry to get back to this so late.

Thanks a lot for this, Coulomb. Really appreciate it 🙂

And your knowledge is truly amazing. I did recently add power-line network adapter in a socket near the inverter to get better network connection for my Pi there. Let me take them out again and see if that brings a change

And also yes, I am controlling the aircons via wifi. Even though this is rather a 3rd-party solution (Sensibo) that is an external IR sender with Wifi connection, which sends IR signal to the aircon - so I would be very surprised if that were the reason (and I've had these for ages and did not notice a problem in the past)

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Hi @Coulomb

a brief update: Unfortunately it was neither the ethernet-over-power adapters nor the 3rd-party aircon wifi controllers 😕 Even when I disconnected power to all of them, the noise was still present

Do you have any other ideas? Do you think that the replacement caps could have anything to do with it? I cannot remember having that noise in the past and am running out of ideas what other changes I have done...

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9 hours ago, wolfandy said:

Do you think that the replacement caps could have anything to do with it? 

I doubt it. If anything, better quality capacitors should improve the situation. That's of course if they used quality capacitors. Can you open the case and get a photo of those caps? They're about 20 x 45 mm or so (not the two really big bus capacitors).

Nothing else comes to mind. Perhaps try to find the source of the sound: heatsink, inductor, ? 

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Thanks Coulomb

9 hours ago, Coulomb said:

That's of course if they used quality capacitors. Can you open the case and get a photo of those caps?

I imported the caps myself for them to use. It is the United Chemi-Con EKZN800ELL182MM40S, which I got from your or Weber's thread on AEVA

9 hours ago, Coulomb said:

Perhaps try to find the source of the sound: heatsink, inductor, ? 

Is there a way to safely remove the cover from the inverter while it is still mounted on the wall and connected? Otherwise it is a bit difficult to do this from outside

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On 2021/01/19 at 8:33 PM, wolfandy said:

Is there a way to safely remove the cover from the inverter while it is still mounted on the wall and connected?

There are just 8-10 small screws; you might need a stubby (short handled) screwdriver or perhaps a Z-shaped one to get to some of them, depending on how it's mounted and what gear is near it. The date sticker will be broken already from the capacitor replacement.

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9 hours ago, Coulomb said:

There are just 8-10 small screws; you might need a stubby (short handled) screwdriver or perhaps a Z-shaped one to get to some of them, depending on how it's mounted and what gear is near it.

Thanks Coulomb

I will see if I can find time over the weekend to tinker with the system

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