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Forum Index : Electronics : Inverter building using Wiseguys Power board and the Nano drive board

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KeepIS

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Joined: 13/10/2014
Location: Australia
Posts: 1828
Posted: 10:24pm 07 May 2025
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  phil99 said  As with FET cemetery's issue a DC ammeter in series with the primary may help see what is happening.


I have a DC amp meter measuring current in the Primary?

Any attempt to use a resistive ammeter will fail, 20kHz components and hard switching noise levels are extremely high, only a differential probe combined with a fully isolated DC hall sensor will give a clear display of current.

And, the current sensor is indicating the beginning of saturation.
NANO Inverter: Full download - Only Hex Ver 8.1Ks
 
mab1
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Joined: 10/02/2015
Location: United Kingdom
Posts: 238
Posted: 10:41pm 07 May 2025
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I'm thinking Phil's thought is to put a dc ammeter in the ac primary cct?

Should read zero unless there's an imbalance in the ac drive?
 
wiseguy

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Joined: 21/06/2018
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Posts: 1198
Posted: 10:51pm 07 May 2025
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I accidentally posted in the middle of an edit from a couple of posts ago and am pasting it completed here as it is now on the previous page and would probably get missed

  wiseguy said  
  KeepIS said  A VERY quick Look at Induced buzz:
Put a 1uf across the AC output and the spark does the same thing, it stops the buzz.

Place a microphone near the toroid, if it hears a buzz, close a relay that applies a momentary capacitor across the secondary lol  

I would have expected the momentary capacitor would have a 50% chance of curing or continuing the buzz. Is it a resonance issue with the main components (culprits) being transformer choke and output capacitance and adding the other capacitance reduces the Q (detunes it) back to the edge of stability?

I have not experienced this issue exactly as described. When my Toroid has a buzz or hum episode it drifts in and out at random but it never stays for any length. Fascinating that a momentary capacitor connection will "fix" it.

Maybe in software at idle we could employ an MPPT - minimum power point tracking that can toggle (suppress) one or two of the narrowest SPWM bits on the appropriate half sine to keep the core magnetics (in a dynamic loop) balanced near to the mid point.  Maybe the noise - which does not appear to do anything bad - and only occurs at no/low loads should just be ignored? We might kill the patient whilst trying to cure it.

Edited 2025-05-08 08:53 by wiseguy
If at first you dont succeed, I suggest you avoid sky diving....
Cheers Mike
 
phil99

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Joined: 11/02/2018
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Posted: 11:14pm 07 May 2025
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  Quote  I'm thinking Phil's thought is to put a dc ammeter in the ac primary cct?
Should read zero unless there's an imbalance in the ac drive?
Yes, that was the idea and as pointed out by KeepIS the 20kHz issue means it would need to be an old analogue type.

An automotive centre-zero moving magnet type would do. They don't use a shunt, just connect in line. Not very accurate but that doesn't matter for this.
 
KeepIS

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Posted: 11:41pm 07 May 2025
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It would likely indicate the small positive hump detected at zero crossing seen by the DC Hall sensor.
NANO Inverter: Full download - Only Hex Ver 8.1Ks
 
KeepIS

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Joined: 13/10/2014
Location: Australia
Posts: 1828
Posted: 01:31am 08 May 2025
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The buzz is independent of the Nano AC regulation loop:

Starting with an induced Buzz at 53V supply in Test Mode.

Very slowly lowering the DC voltage will hold the buzz down to 33V input, 99% PWM and 7 volts DC below AC regulation.

Slightly below 33v, Buzz stops and cannot be induced at these low voltage for obvious reasons. The small current hump causing the buzz is in ONE side of the AC zero crossing cycle.

Controller in RUN mode:

Sometimes a slight buzz appears during soft start ramp-up and then disappears, at PID handover there is no Buzz and idle is quite.  

Again, a sudden DC disturbance will induce a Buzz, restart inverter and all is quite again. However the inverter is more resistant to Buzz from small DC step changes when the Nano is in PID control AND AC is regulated.

@Wiseguy:

I agree with your thoughts, I wonder if we are just trying to heard cats again?

I can only speak for the Main Inverter: I would not change a single thing, the layout, wiring and assembly is the result of eliminating all of the unforeseen errors and mistakes I thought I have allowed for in my first few inverter builds.

The Test bench unit is a lash up, controller way to close to the power board, choke cabling close to the controller board, slightly incorrect chokes, Toroid not wound correctly and more, but even then it runs quite well in this compromised state.
.
Edited 2025-05-08 13:22 by KeepIS
NANO Inverter: Full download - Only Hex Ver 8.1Ks
 
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