Guru
Joined: 13/10/2014
Location: AustraliaPosts: 1769
| Posted: 06:08am 02 Jun 2023 |
Another twist in the Choke "who done it" story.
But first, I've modded the front panel to fit an analogue Meter to show Peak input current, when I'm finished it will be able to switch to show kW input as well.
I'm glad I left the finishing of the cabinet until everything is set in stone. Moved the twin 15A socket to the RH side, a much better location IMHO. I didn't want to leave the AC skt off as it allows testing the inverter off load, and also makes it self contained, needing only DC input to power something.
The power point moved to fit an Analogue Meter. The socket above the Meter is the same as the DSO skts. It brings the DC Current Sensor output to a location where the DSO can be plugged in with a patch lead without opening or disturbing the inverter.
Power socket now mounted on the RH Side of the cabinet.
Skts above batteries are used when testing.
The Choke Story continues
The Current drawn by the big 380A to 560A loads has dropped slightly by 5A to 15A, the Power input remains the same as the DC input voltage across the FETS is now higher and therefor less current is needed to hold 230Vac output.
The Startup noise from a sustained 375A current surge lasting almost 2.5sec was very quite before, however it's now even more subdued in tone, to the point that I would hardly notice it while I'm sitting in front of the Inverter with the inverter door open eyeballing the Toriod.
Who knows? on that one.
Choke Inductance requirement has changed slightly?
The Inverter AirCon is just audible now, and I mean just!
The other bad loads are slightly more noticeable, and there is a slight 1 or 2 cycle ringing on the Step in distortion in the AC waveform, as I posted before, it's the level of ringing here that determines how loud the Toriod screams in my build.
The other bad loads [Hair straightener and Heatgun on low] have a very slight buzz, it's just like the Choke inductance now needs to go another 1 or 2uH lower.
Talk about getting close to the 37uH value I had, but I'm glad I'm sneaking up on it this way as this is very revealing.
Trying to get a one size fits all "FOR TORIOD NOISE", is almost impossible, but for each individual inverter it's possible and worth pursuing. Especially as the multi Toriod Ring chokes are so easy to wind 4 turns through, just change the number of rings for slight inductance changes, or a turn for bigger change, or in combination with a one turn change to move the inductance up or down.
When selecting a Choke for a new build, I would still start out at around 40uH [at least 300+A saturation] and then work a few uH up or down when testing a bad load, or make one by inserting a Diode in series with a heating element, like a lot of the equipment approved for use in AU have used.
What Changed
In my system, the R-Loss in the Fuse holder was removed, now DC input voltage only drops to 50V instead of 46v to 47v under high 300A+ current. But appeared to change the Inductance requirements slightly? Strange as some of the noisy loads are only in the 300W to 600w range, the Aircon is in the 2.2kW range.
Then I remembered that not only did I strip and rebuild the DC input terminal connection plates, I also did the same to the Choke connections, and for good measure I removed and rechecked the connections to the Inverter Power board.
That was enough to remove a slight R-Loss (I know because the choke connections are now cold under very high power), the change in R-Loss was enough to slightly change Inductance requirements, also this is likely the same reason for that big sustained power-up load being more subdued now.
I feel it's important to remember that the noise in my inverter is only noticeable on the very worst of AC distorting loads, and most times people just avoid these loads with their inverter, but I now test with them every single time I make a change.
When you get everything set up in your inverter, and have these loads making nothing more than a low hum at most, you have a benchmark to use every now and then without opening the inverter. It appears to me that any change in the wiring, chokes, toriod or drive circuity will be noticed first with these loads [buzz hum], and perhaps a sign to check the inverter, tighten connections etc.
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Edited 2023-06-02 16:15 by KeepIS