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KeepIS Guru Joined: 13/10/2014 Location: AustraliaPosts: 1679
Posted: 05:57am 17 May 2023
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Now that the Inverter is running perfectly, I decided to get some Data on the DC input currents for this inverter Board compared to the Standard 8010 driver board.
The results are interesting: The Test setup is the same as before:
1: A 500A C2T unidirectional Hall Current Sensor. 2: 100Mhz DSO.
A: The DC input waveform was very clean compared to the Old Driver. B: The Current drawn was a bit less on the Dust extraction. C: I have to investigate further (not going to speculate) on the initial start up Stall surge current.
It appears that when the stationary induction motor and load are dumped across the inverter, for the first cycle the peak surge current starts out low and builds to maximum start surge current by around the 4th cycle. Not so much of shock to the FETS.
Below: This is the compressor startup - 535A - 21kW The 5 tiny pulses at the start are around 350 watt general running load, then the 3HP Compressor is powered on. The very sensitive LED fluros give a momentary tiny flicker.
Below: This is the DE startup - 392A - 18.2kW This is slightly less then with the old inverter driver. The 4 tiny pulses at the start are around 350 watt general running load, then the DE starts up.
Below: This is the DC current waveform into the inverter running at 534A and 21kW of load: Each cycle is one half of one AC sinewave, two DC cycles for 1 pos to neg excursion.
The repetition rate is 100 x 540A pulses per second of peak DC current.
.It's all too hard. Mike.
KeepIS Guru Joined: 13/10/2014 Location: AustraliaPosts: 1679
Posted: 06:10am 17 May 2023
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The following shows the duration of the load start up and it falling to Run current.
The compressor - 530A DC input, that peak load is around 600ms long before it drops off.
Below: Part of the DE load with what looks like FET drive waveform ripples in the Image.
The complete waveform (this is only a portion) is almost 3 seconds long of 392A / 18.2kW needed to start the DE. (Exactly the same time as on Mains AC)
.It's all too hard. Mike.
KeepIS Guru Joined: 13/10/2014 Location: AustraliaPosts: 1679
Posted: 06:54am 17 May 2023
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I mentioned the Big Power board capacitors feeling slightly warm in a previous post.
Out of interest I added two more for a total 60,000uF, these screw terminal caps have a high current rating far in excess of the China inverters total capacitance.
What I notice appears to be because of wiseguys great design, mounting the backs of the FETS against very thick wide copper current buses on the Power board. So the FETs are clamped between the Heatsink and the power Boards Copper buses for extra cooling.
The slight few degrees temperature increase in the FETS, is, over time, slowly transferred from the back of the FETS through the Copper buses to 6 x thick high current standoff screw connectors to each CAP PCB, then transferred through the Cap screw terminals into the outer housing, that's the slightly above ambient warmth I feel.
The caps in this design are mounted completely out in the open, there is nothing around them and NO real heat generating source in the Inverter and controller DECK in the cabinet.
The FANS have not come on at all today, and trying to measure any real temperature increase in the Caps is difficult because it's so little, but by touch I could feel a slight warmth. So nothing to see here.
Do I sound a*n*a*l, maybe, but as I finalize the build, I want to make sure everything is as it should be. I am keeping an updated copy of this build thread for my future reference, it's kind of a blog, a memory refresher for if / when something does go wrong in the future. I hope this post made sense. . Edited 2023-05-17 18:14 by KeepISIt's all too hard. Mike.
KeepIS Guru Joined: 13/10/2014 Location: AustraliaPosts: 1679
Posted: 02:14am 18 May 2023
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Some Choke testing no load, 350w load, 2.3kW load and 12kW startup load.
To cut to the end, the choke requirement remains the same, but minor improvements to the waveform can be noticed at Idle without the Ferrite 1/2 of the Hybride choke.
Bypassing the Ferrite makes a slight change to a small kink in the Leading waveform of the DC current input swing, but that's it.
This inverter uses two chokes, one in each leg of the Toriod.
Choke A: Hybride of Ferrite E-Core at around 16uH and a Toriod 4 stack of 16uH in series for a total of 32uH, saturation around 180A from memory.
Choke B: 37uH 10 Stack Toriod that does not Saturate even at 600A.
Light loads (350W) shorting out the Hybride makes a minor difference to the waveform. Shorting out the 10 Stack makes almost no difference.
2.3kW loads. Shorting out the Hybride makes a difference, the waveform is not as crisp and the DC input waveform is slightly distorted.
Bypassing the 10 Stack choke is a bad idea, DC input waveform is pulled and leans a little, AC output is still fair but the Toriod is not happy, changes from silent to a slight buzz at 2.3kW load. (that's with the hibride 32uH still in circuit.
The photo of 2.3kw load, AC output (blue) over DC input current waveform (yellow), notice the DC input waveform is twice the frequency of the 50Hz AC output.
1: The Flat top on the AC is from the Loads, not the inverter. 2: The Mains AC powering the same loads is exactly the same.
Running at 2.3kW:
12 kW startup: The AC and DC input waveforms are both perfect under 12kW startup loads.
Finally, thinking about the apparent first few cycle of DC input soft start waveforms I posted.
I think I'm been deceived by the caps. Could the Big Capacitor bank may be supplying most of the startup current surge for the fist cycle, a bit less to help the next 2 or 3 cycles before the DC supply takes up the full load. That would explain the waveform on the Battery supply cable. I'm going to verify this later today.
EDIT:
Took a quick snap of the front panel after an hour running at 2.3kW to 2.6kW:
AC volts: 228v DC power: 2.38kW AC power: 2.24kW
This is a complex load so not that accurate to calculate efficiency.
Note: No Fans running or started since yesterday morning, it's been running all night and day leading up to the hour long workshop gear being used as above.
Core Temp: 31 deg Heat transfer Bars: 25.7 deg
Yellow: DC input current waveform Blue: AC out to load.
The 3 position switch with Black silver knob is: OFF - AUTO - ON
In AUTO, the Inverter is started and stopped depending on the state of the Public AC supply [mains]. It's automatically transferred from Mains to Inverter [Mains Loss] and back, depending on the Priority switch setting, [Mains or Solar priority] transfer is via an external Transfer box.
Top Green LED: AUX 20V indicator, also indicates AC output from the toriod.
RED LED: 8010 Status LED
Green LED/push switch, next to RED LED: Over current trip LED indicator and reset switch.
. Edited 2023-05-18 15:57 by KeepISIt's all too hard. Mike.
Revlac Guru Joined: 31/12/2016 Location: AustraliaPosts: 1024
Posted: 08:25am 18 May 2023
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I was thinking about this yesterday and it looks like it might be a good thing.
Looking at your choke arrangement, I might try the same idea (or similar) on my next inverter, but it depends on what parts I find, we use different parts building these things, so results may be different.
Do you think a gap between some Toroid rings would make any difference to saturation? I probably got the wrong idea.Cheers Aaron Off The Grid
KeepIS Guru Joined: 13/10/2014 Location: AustraliaPosts: 1679
Posted: 09:56am 18 May 2023
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No, you don't need to space Toriods, these are low cost in any case, and a lot of inverters do have them. I had around 16 from the early SunnyBoy inverters I think, usually had chokes wound 2 or 3 stacked at a time.
I can only repeat that both Inverter drivers just love that 10 Stack toriod choke, especially under high power. I would not be game to start the big loads without that in circuit, and looking back to the first power up of the single toriod transformer on the bench, I had made a 6 stack toriod choke before I moved on to any real power testing with a battery bank. This could be in part, one of the reason I have not nuked a single FET ----- Yet.
I've been looking at waveforms again, Primary current, and Across the drive output to the Toriod transformer, but dam you have to careful, a Digital DSO can lead you astray with the way they trigger and display the waveforms. You can end up chasing something that's not really there. I'm sure the real expensive units are a lot better, tomorrow I'll get out my Analogue CRO with Digital storage and make sure of what I'm looking at, that can't and never has fooled me.
It seems to me that the choke setup, and the values I have chosen, seem to be hard to beat. In both types of inverter driver configurations, I had expected to find this as it's not a black art. If there is no underlying wiring error or fault in an inverter that you are trying to cover with a choke, then the values, the reason for the choke, and why they work, should not change..
However I think the Ferrite E-core might be slightly increasing the Decaying sinewave I posted earlier, when the Drive is abruptly stopped at power off. However it appear to be completely harmless.
It's hard to catch, and I've been lucky enough to catch it again while monitoring the drive to the Toriod and AC output, both locked and gated, even have a screen capture.
It has confirmed that the ringing is solely in the Transformers decaying magnetic field. . Edited 2023-05-19 09:39 by KeepISIt's all too hard. Mike.
KeepIS Guru Joined: 13/10/2014 Location: AustraliaPosts: 1679
Posted: 01:29am 19 May 2023
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This is the ringing in the Toriod at the point when SPWMEN is driven LOW.
I've never caught it at Crest disable before, looks to be around 1kHz. Toriod does not make a sound, No Load. Likely it would be swamped with a load.
When you think about it, after 10ms the ringing is virtually nothing, about half of an AC cycle.
Yellow trace: Between the HI/LO drive feeding the Chokes and Toriod transformer.
Blue: AC output after mains filters.
BELOW: Startup AC voltage against DC input current
Blue: AC output to load.
Yellow: Unidirectional 500A DC HALL current sensor on DC input to inverter.
The point of switch on is the little dip in the AC (twin peaks) then the current starts to rise "the secondary AC trace will see it first".
The AC recovery seems to be pretty good, and after a few cycles it holds that for 2.5 seconds as the Load current increases for a few more cycles then (not shown) stays constant at 400A @ 100Hz peak DC swings, one for each half of the AC cycle.
The slight distortion on the AC waveform disappears in a few cycles and becomes a near perfect sinewave after that.
12kW start from Induction motor.
. Edited 2023-05-19 17:44 by KeepISIt's all too hard. Mike.
wiseguy Guru Joined: 21/06/2018 Location: AustraliaPosts: 1156
Posted: 08:26am 19 May 2023
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Stop poking around in there !!
I agree about the few cycles of 50Hz current buildup as being related to capacitor storage.
I was also wondering about the offset of the current peak to the ac voltage waveform peak. I reckon that is also an artifact of the capacitor bank?If at first you dont succeed, I suggest you avoid sky diving.... Cheers Mike
KeepIS Guru Joined: 13/10/2014 Location: AustraliaPosts: 1679
Posted: 09:14am 19 May 2023
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I agree, when you combine the slow build and offset, the dots start joining together.
I know it was half tongue in cheek, but the beauty of a current clamp and the bridge outputs being on those wide copper straps joining the top and bottom decks is that I don't really have to poke, which is a good thing. As I'm tiding up the interface section above the inverter power/ driver deck, I thought I'd have a look at the relationship between AC voltage out and DC input current at load start.
Mike it's been running night and day, slightly cooler weather and not a single fan start up.
BTW the growl at startup that you were hunting down, there is a slight growl sometimes, but only audible sitting in front of the inverter, but it goes dead quite after a few seconds. My wife spent the day working with all manner of power tools and there wasn't a peep out of it. Equipment loads were 1.6kw to 2.8kW running, some times a couple at a time, I'm on the Computer and nothing, even starting the big DE at 12kW. The only indication she had started a big load was a flick from the LED fluros.
Those stupid LED fluros blinking, I only realized today that it's exactly the same on mains AC. Things you never notice before until you start looking for it.
Really impressed, hope you are enjoying a change of scenery . Edited 2023-05-19 19:14 by KeepISIt's all too hard. Mike.
wiseguy Guru Joined: 21/06/2018 Location: AustraliaPosts: 1156
Posted: 01:00pm 19 May 2023
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Some time ago when you mentioned flicker I had wondered if you had tried out those loads on mains and watched the lights lately.
My “change of scenery” currently is in a caravan park in Broken Hill, stuck here with a broken wheel. The notorious Barrier “highway” ( half goat track complete with goats kangas & emus) has claimed yet another victim. A big bang as the alloy rim split down the Centre and lots of stuff spewed out behind the van severing the electric brake wiring as it went. I have now fixed that. Of course it was an odd size rim that will take until next Wed onwards to come from Sydney. C’est la vie …🙄. I was hoping to be in Port Douglas by then - it is so cold here ! I’ll post all the holiday pics here soon too lol - end of distraction to topic - sorry for the wander. Edited 2023-05-19 23:01 by wiseguyIf at first you dont succeed, I suggest you avoid sky diving.... Cheers Mike
KeepIS Guru Joined: 13/10/2014 Location: AustraliaPosts: 1679
Posted: 10:24pm 19 May 2023
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I can't believe I never noticed it before, well I can actually, I get so totally focused on something to the exclusion of everything else. I'm sure that's a behavioral condition of some kind
Seriously, I thought these thing only happened to me, dam, well I hope that's the last of it, but, don't these things always come in groups of three ?
Smooth sailing . Edited 2023-05-20 08:24 by KeepISIt's all too hard. Mike.
analog8484 Senior Member Joined: 11/11/2021 Location: United StatesPosts: 108
Posted: 05:17pm 20 May 2023
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What's the main reason for the different choke material (and size to a degree) between A and B? Is it due to the PWM modulation scheme?
KeepIS Guru Joined: 13/10/2014 Location: AustraliaPosts: 1679
Posted: 11:10pm 20 May 2023
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I found that Ferrite E-Core appears to behaves differently for the same value of inductance with very Hi frequency transients.
The toriod core being a mix of iron, silicon and aluminum, and made with a distributed air gap in some cases.
Toriod chokes:
Stacking 10 small toriods = less number of turns for the same inductance, and therefore allows using thicker wire to pass through the small inner diameter of the toriod, and more cores = higher core saturation for a given inductance.
This ends up with a powerful choke having a smaller footprint, and in reality is a very compact choke for the current capacity and saturation levels obtained.
The E-Core saturates quickly, like 30A to 60A. I use it to catch the FET HI frequency switching transient currents, especially at idle, then the choke basically disappears when it saturates under loads, the 4 stack Toriod also saturates at around 120A (from memory).
I refer to the Hybrid as one choke.
My thoughts are: At idle and low power, the two Chokes have around 73uH, idle switching transients are taken care of, and High power switching transients are buffered from the BIG Toriod transformer under brutal high power surge loads of over 24kW DC input. The 10 Stack core does not saturate at that level, the Hybrid choke is basically a piece of wire above 180A.
Changing Modulation schemes did not change the choke values or design in my system, and testing showed that nothing needed to be changed after I updated the Inverter Controller and Power stage. . Edited 2023-05-21 09:13 by KeepISIt's all too hard. Mike.
KeepIS Guru Joined: 13/10/2014 Location: AustraliaPosts: 1679
Posted: 02:02am 21 May 2023
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I left the previous post as is, it shows that eventually you will find a load that really helps you make the final choice for a Choke, but for different reasons, it also shows IMHO, that something like a 10 Stack Hi saturation 37uH choke is the starting point to work from, play all you like, as I have done, but I would never run my inverters without that choke.
Soooo... right on Que, I finally find a load that behaves differently on the New Inverter Controller.
The Air-conditioning unit in the workshop: A Fujitsu reverse cycle Inverter.
First time running this inverter, it's cold today: I was out of the shed when it ramped up, my wife came over to tell me the AIR Con was making a loud buzzing noise and something was beeping.
The Chasepower UPS which keeps my programming PC and two 32" monitors running no matter what, was having a hissy fit and was the cause of non stop beeping, it's very sensitive, there is a name for that now but I'll stay within the bounds of political correctness.
It was the inverter that was buzzing loudly, AC power out was around 2.3kW, lots of other light loads running as well.
Temps were normal, DC input current was fine, everything was electrically happy.
Put a DSO on the AC out and had a waveform similar to the Heat-gun pulling power from one half of the AC cycle, it has a Diode in series with the Heater winding on low.
It was also ringing at the point of waveform disturbance. I've posted a picture previously, that time, nothing I did made any real difference to the waveform, however this time there was big difference when testing choke combinations.
Bridging out the 4 stack toriod part of the Hybrid choke, leaving just the Ferrite choke in circuit, and it made a bit of an improvement and quietened the 3 stack Toriod transformer about 30%, bridging out just the Ferrite E-Core made a huge difference and reduced the buzz considerably more - both chokes are around 16uH.
Once again that difference between choke materials.
I bypassed the Hybrid completely: The Transformer was silent, the waveform was almost normal but for a very slight kink on the affected part of the cycle.
Primary current went up a fraction when the Hybrid was bypassed, the inverter was running at 2.3kW as I was testing the combinations.
Switched off the inverter and bypassed the Hybrid choke correctly, then powered it back up.
Silence.... with the AC and 2.3kW loads running. I took the gamble and started the Dust Extractor, that's a 400A DC peak input - 12kW AC on top of the 2.3kW Inverter load.
Perfect... Not a peep from the UPS, the toriod transformer gave a gentle hum just at the start of the 2.5 second duration 12kW surge load as it was dropped on to the 2.3kW running load. Final running load with Dust-Ext spun up was 3.8kW, the Inverter is silent.
NOTE: I had determined on previous tests that the Ferrite E-Core was causing the ringing in the transformer at power off to be SLIGHTLY increased, but as it appeared to be the only effect, I wasn't going to remove it.
EDIT: In the NOTE above, the difference I saw was because the cutoff point was slightly lower when checking. I have just tested the Transformer ringing when SPWM output is disabled on power down, there is None, Zero, and NO change at all to the ringing as the Transformer field collapses "under no load".
Under load, the oscillation [ringing] is quashed. Currently my inverter output automatically switches to Mains when it's powered off, a possible reason why I noticed this and Mike didn't? Mike [wiseguy] has the only other running inverter controller and power board like this, it's his design, but he's had little time to fully play around with it..
So ... The Chokes were innocent.
The Take away: The overall sweet spot for this inverter driver is now: One 10 Stack 37uH choke with a saturation point higher than 540A peak DC input, I believe that the FET switching currents could be a lot higher than this depending on the % of PWM drive width [on time] and like almost everything else, that varies with each inverter build configuration.
BTW None of the other newer "inverter drive white goods" and other equipment has caused any issues, not even our big inverter microwave, only the AIR-Con pushing HOT air. . Edited 2023-05-21 16:10 by KeepISIt's all too hard. Mike.
Revlac Guru Joined: 31/12/2016 Location: AustraliaPosts: 1024
Posted: 08:30am 21 May 2023
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Thats interesting, I Didn't know the inverter aircons were like that, I have only run the old standard type aircon, I'm going to fix my heat gun so it can be used on any inverter without problems. Will remove the diode used for low speed and just use the high speed setting, and run it with a 10kw SCR Motor Speed Controller for variable speed, I better test it to see how it works.
Unwound the copper wire from a few of those toroid chokes from a GTI, fingers are a bit torn up sharp enamel coating, will toughen up a bit after a few more. Cheers Aaron Off The Grid
KeepIS Guru Joined: 13/10/2014 Location: AustraliaPosts: 1679
Posted: 09:00am 21 May 2023
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I have been informed by my wife that the AirCon has not run on Heat with the previous inverter board either.
I found the really bad noise was only there at max current into the AirCon [Heating happens to have the highest current draw] so it's likely not not the inverter driver difference.
It's just something I have not encountered before, we normally only cool the shed up until today, and likely due to the testing I was doing with the Hybrid choke.
Note that even using the extra 4 core stack choke of 16uH also causes this noise, so a single choke is all I'm using. And below is some indication of starting the big loads with one V two chokes.
So, for anyone interested, this is the difference between starting the 3hp Dust extractor with the hybrid choke removed, not quite the same time frame, but it's still interesting.
Blue trace AS output.
Yellow trace DC input current:
The first capture was centered (AC coupled) with the AC sinewave, the second was DC coupled, this is a unidirectional DC Sensor, so it only produces output in one direction, each vertical division is the same value in both.
The extra choke was definitely reducing surge current and changing the ramp up curve, at the same time making the AC output go a little strange.
Below: Two Chokes start up:
Below: One 10 stack 37uh choke, this is what I'm using now in the inverter:
I have also started the 3Hp Compressor at 530A DC input, it draws more current on the first 2 cycles with one choke, but it's a very clean start and the UPS does make it's normal beep of complaint. Very impressive - no smoke ........... yet! .It's all too hard. Mike.
KeepIS Guru Joined: 13/10/2014 Location: AustraliaPosts: 1679
Posted: 09:08am 21 May 2023
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Yes isn't that a pain, my hands hurt for a day or so.
BTW I forgot to answer a question about those small isolated DC-DC boards, I bridged a resistor between two points and got it to startup perfectly instantly every time at 42V, I'll post a picture if you like.
I'd say that the Heat gun and diode is not causing to much distress to this inverter now, bypassing the other choke with heavy cable has improved that as well, but I had to do it properly to get the full effect.
Will be interesting to see how a zero crossing SCR will go, it's still a form of phase switching and inverter may still complain, let us know if it helps and I'll do the same.
EDIT:
Looking at the screen captures of the Choke startup compassion, the slope of increase in current is about the same, using AC coupling for the Sensor is just causing it to float around as the DC level rapidly changes in the first capture, but the main point was the difference in current over the first few cycles. . Edited 2023-05-21 19:28 by KeepISIt's all too hard. Mike.
rustyrotors Newbie Joined: 07/01/2023 Location: United StatesPosts: 36
Posted: 03:35pm 21 May 2023
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was the buzzing coming from the e-core choke or from your 3-stack transformer?
when i was experimenting with chokes, i noticed my e-core ferrite would buzz and cause nasty higher freq waves riding in the AC output if not clamped together very tight. clamp the e-core tighter, buzzing would go away and AC output would be much cleaner. I suspect loose clamping causes the e-core gap to vibrate also, with primary current, which would also vary inductance, causing waveform to distort. i wonder if that was happening, which was somehow causing a weird effect or resonance where the e-core is not just a low value resistance at full saturation
I now just run stacked powder iron toroid choke, a pair of T250-26 which run silent, no vibration. although slightly higher idle draw than with the ferrite e-core. i may stack a couple more like you did
analog8484 Senior Member Joined: 11/11/2021 Location: United StatesPosts: 108
Posted: 04:33pm 21 May 2023
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That's interesting. At 37uH you are much closer to the often recommended 47uH choke value. I guess the A/C is a large non-linear load that was probably starved of current by the large choke assembly and caused voltage waveform distortions that in turn freaked out the UPS's.
Have you seen any noticeable difference from different choke placement between the primary legs?
KeepIS Guru Joined: 13/10/2014 Location: AustraliaPosts: 1679
Posted: 10:49pm 21 May 2023
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When I use ferrite chokes they never vibrate as I take measures to ensure that they don't.
BTW A Ferrite choke in series with a small value of Toriod choke usually won't make any noise at all and as a bonus runs cool.
I'm sure I said it was the Toriod making all the racket. The chokes are always silent, including the Ferrite E-Core. I found from the first time I started using Toriods chokes that they were silent, and if made correctly, any real heat is generated by the winding only.
Over the years there has been many discussions about that 47uH value, it was a figure that seemed to be a good starting point, and it's also the value that most Chinese inverter boards recommend, which doesn't mean much, but in reality it's a ball park value.
BTW, there was no change in idle current between a Ferrite E-core and a Toriod choke in both of my inverters. I have made many variations of E-Core chokes, including double and triple cores with various size Gaps in testing saturation and inductance.
Nothing is starved of current in this inverter. It is an interaction of resonance, current and magnetics between the choke, Toriod transformer and load with phase switching / controlled loads of any kind.
I have spent months testing with various loads, not something that is easy to do in a home workshop with limited load variation availability, and then testing every combination of load with every choke design, configuration and wiring variation.
Small 600W loads can cause the same thing as a 2.3kW of reverse cycle inverter Air-Con that ONLY misbehave on reverse cycle ramped up to MAX Heat, never on Cold cycle.
The UPS is incredibly sensitive to the Voltage drop and the low volt detect is only a few volts below 220V, I'm running the Inverter output at 227V to 230Vac, so any transient glitch will set the UPS off.
I think of the UPS as the canary in my Coal mine.
There is a bit in the standard Controller, almost no difference with this new design, one of the reasons some of us put a choke in each side, but I'm running only one now and there is absolutely no difference to Idle current and idle waveform.
BTW May I make a suggestion, it might be better to edit or cut a big quote down in size when replying, I find it takes up needless space in the reply and tends to make the thread seem a bit duplicated. Not meaning to offend you with that suggestion. . Edited 2023-05-22 09:12 by KeepISIt's all too hard. Mike.
Notice. New forum software under development. It's going to miss a few functions and look a bit ugly for a while, but I'm working on it full time now as the old forum was too unstable. Couple days, all good. If you notice any issues, please contact me.
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