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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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Posted: 06:45am 08 Sep 2024
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Thanks Aaron, and others who have sent me a PM or email.

I've been tuned-our for some time now with the New Inverter, still some tiding up and testing to do, but gee it's getting better by the day - and here is why:

For some time now in the last Inverter and power board, I've been chasing some high frequency noise and ringing, this followed across to the New dual inverter, the boards only have ferrite beads on one side in both boards.

So I wanted to try the power board's with all ferrite beads fitted, see if it makes a difference.

In the dual inverter, the noise appeared to be more noticeable from one power board, but due to the radiating nature of this noise, it was proving hard to pin down.

I spend the past couple of days building two new power boards, the ferrite beads I used are not as thick or as long as wiseguys original, so inductance will be different, but these beads should make some difference, and they allowed me to mount one power board straight to a big flat heatsink, so didn't need to build up a set of spacing bars.  

Test mode is your safety net for testing without damage, use an adjustable power supply, I set the current limit to around 400ma, and start the voltage at 10V and slowly increase it looking for any sudden jump in current, the LCD will indicate some AC output even at voltages around 13v to 16v.    

I found one power board made the Test Inverter setup draw twice the idle current, as the other board, I traced that to an incorrect resistor value on one Opto coupler  

The result is the waveforms are now really good and all the noise has gone, but more testing will be needed to see the real impact of the ferrite beads, and if the smaller beads are suitable.

A benefit of reducing the noise, the idle current is now slightly less.

The Inverter idles at 47 Watts:

With the boards installed in the new Inverter, the power difference between AC outputs on each toroid is now almost impossible to detect on dual AC power monitors, even at 3.5kW, both AC currents and powers are now virtually identical.

I've hit the new boards with over 712A total Peak DC input and all I got is one little flick of the LED light above me.

The really interesting thing - I sat beside the Inverter when it started the Extractor at 500A peak DC input for 2 seconds, the Toroids were "absolutely" silent with the new boards starting that load, with old boards the toroids made a slight buzz with very high current startups.  

So there are a number things I need to investigate with the old boards, at least I can take my time now.

FYI:

Current sensor on the DSO are now really clean, DSO captures of the compressed startup current waveforms are now a clean smooth envelope.

Old boards 240A per power board (480A total input):


New boards:


Old Boards : Current sensor zoomed


New Boards:

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Mike.
 
KeepIS

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Posted: 12:21am 09 Sep 2024
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Just did the Harmonic distortion set with the HIOKI Power Quality Analyzer.

Power to the property with all normal loads running:

Total Harmonic Distortion:

Mains: 2.5%

Switch to Inverter (20ms):

Inverter: 2.3%  

Virtually the same first 5 odd harmonics and all below 2.3%.

EDIT: 1.6% with an extra 1kw resistive load.

As I found with testing on the single stage inverter, the THD is dependent on the loads, any load causing distortion in the AC supply will obviously increase THD, that is a load distortion not the Inverter or Mains AC, both will distort.

At the moment I haven't tested the dual Inverter unloaded or with a simple resistive load, I'm sure it will be below 1% as it was before, something for the To-Do list.    

   
_
Edited 2024-09-09 11:03 by KeepIS
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KeepIS

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Posted: 04:36am 10 Sep 2024
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FYI: The Inverter running separately at Idle and Loaded : AC Total Harmonic distortion.

No Load 0.9% THD  

2.3kW Jug (resistive load) 0.6% THD.

Almost all fundamental frequency, the first and second odd harmonics are tiny, the third barely visible, nothing after the 3rd odd harmonic, this tester reads out to the 37th harmonic.

These are seriously impressive values for an Inverter.

BELOW: AC waveform @ 2.3kW, it looks the same at Idle:

When I switch a 2.3kW load onto the Inverter running at idle, the AC drops half a volt.

I'm measuring AC at the end of an extension lead and plug board across the 2.3kW load.

The only visible change captured on the DSO is that slight half a volt drop across the lead to the 2.3kw Load.    
 

_
Edited 2024-09-10 14:37 by KeepIS
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KeepIS

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Posted: 09:17am 11 Sep 2024
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Finished the Triple multi function AC output monitor.

It's that black housing on a tilted stand that sits on top of the Inverter, the stand simply slips over the rear top section of the Cabinet.

I wanted all AC wiring to take a direct path straight out the back of the Toroids, these and the 4 chokes and AC filters sit in the bottom of the cabinet. I'm Trying to keep Inverter HF noise from the choke cables and DC "cables" from radiating into the AC, especially after it had gone through the AC filtering stages, so no AC monitors or wiring in the wiring looms or anywhere near the Front Control panel.

Power stage 1 AC on the Left, stage 2 AC on the right and combined AC power & current in the center.

BTW that's showing a power stage delta of 48 Watts at almost 5kW, it varies between 28w to 48 watts at 5kW as the AC meters have different sample and update times, and the load is varying slightly.

It's now evening and the Inverter has been at 5kW for 45 minutes, up from it's normal daytime 1kw to 4kW, heatsinks sit at room temperature all the time (28° to 29° ATM), both Toroids still at 31°, they vary between 31° and 35° throughout the day - the Toroid cooling fans have not come on as yet in this dual power stage inverter.


_
Edited 2024-09-11 19:43 by KeepIS
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wiseguy

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Posted: 10:13am 11 Sep 2024
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Does this have the Auto switching PCB functioning or is that still a work in progress ?
I know there are a few (including me) waiting for the news on whether its a goer or not.
Congrats on your build it has everything and then a bit more....
Easy to work on and also see exactly down to minute detail what it is all up to.

I have tested the first stage of my 3KW toroid/inverter. Idling power with all running appears to be ~ 18W but I will confirm more later. Just the power stage without including the Controller/LED display & Kilovac's consumption is ~ 13.6-14W idling.
If at first you dont succeed, I suggest you avoid sky diving....
Cheers Mike
 
KeepIS

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Posted: 08:08pm 11 Sep 2024
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Thanks, I'm feeling a bit guilty now as I still haven't made the 2 stage switch.

I've been tiding up loose ends with build, added the ground plane earth which has no effect in this build - totally different layout and wiring seems to have negated the need for it.

This Inverter will be wired in permanent Dual mode:

My total idle power is 62 watts with everything running, including my SACAF air flow system - "Silent Assisted Convection Air Flow".

It has no discernible impact on overnight power usage with respect to morning Battery Bank SOC "state of charge".

FYI For some time now we had stopped starting the bigger workshop machinery on the single inverter, yes it could do it, but I felt that it was just getting brutal to be continuously doing that.  

We now treat this Inverter the same as the Mains supply - that's how solid it feels and sounds - sounds = absence of any sound - and it virtually runs COLD.

I will try to find time to get the dual stage tested - I've just put the board and parts on the workbench as I write this. Hopefully I won't get sidetracked today.
_
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KeepIS

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Posted: 10:58pm 11 Sep 2024
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A few extras I included which add a little to the total Idle power.

A tiny Fan blows air over the Controller PCB and keeps a small amount of air circulating through the upper cabinet, the air exits above each Power boards and Heatsink.

This removes any heat buildup from the Boards and Caps under higher power 24-7 off grid running, there is no forced air flow of any kind over the Heatsinks, which is why they are mounted vertically on the rear of the cabinet for normal convection air flow cooling.

The Control panel has its own small 75v to 12v supply for all LEDs and Heatsink temp Meters, the LCD has its own +5V supply running from this 12V supply.

The Power for extra current trip boards in the bottom of the Controller cabinet and the Peak meters circuits and +12v to the HALL effect Current sensors come from another small 75v to 12v supply and +5v supply.

This was done to keep the Controller +5V and +12V supplies solely for the Nano and Controller board electronics, and for driving the Six isolating supplies on the Two Power Board via the SPWM drive cables.

The Nano Micro has its DC and Reset lines Isolated from the USB port, ensuring that no external device can accidentally reset or power the Nano, this also stops the Nanos onboard USB interface controller from resetting the Nano Micro.

Every effort was made to keep the Controller supplies clean, isolated, stable and dedicated to SPWM creation and Inverter control at very high power levels.

Doing it this way greatly simplified the wiring and layout, it gave me greater control over the number of ground and DC connections back to the Controller and reduced possible earth loop effects and switching noise injection.
Edited 2024-09-12 09:01 by KeepIS
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KeepIS

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Posted: 04:29am 12 Sep 2024
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FYI When starting the Dust Extractor (about a dozen times today) and the Inverter drawing 540A Peak DC input at each power up for 2 seconds, the shed LED lights don't even "BLINK" with the new power boards.

WTF! Seriously

BTW - I'm working on the 2 stage Test board at the moment.
Edited 2024-09-12 14:30 by KeepIS
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KeepIS

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Posted: 09:30am 12 Sep 2024
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Mike (wiseguy) It turns out I did not have the correct IC:

So, I made the relay and FET switch sections. I used a rotary switch with make before break contacts and Controlled the two relays and FET enable / disable exactly as the IC would have done, but manually.

Good news, it worked perfectly, first with no load on a small PSU and then with 200 watts, all good.

Next nearly 40Kw of batteries:

RE1 inrush current for Toroid PRE-FLUX was around 25A to 40A peak DC, which is not even a tiny SMPS plug-pack, so nothing to me.

When RE2 is enabled along with SPWM enable, there is no DC input current surge or change.        

Next the Inverter running with one stage and 2.3kW of Load:

Pre-Flux gave a "tiny" flick of the DC meter above the 2.3kw Load line, then full load was smoothly shared by each stage.

The only indication of switching from 1 to 2 stages and back at 2.3kW, is the smooth rise and fall of the AC current sharing readout and the smooth transfer of current sharing between the Peak DC input meters. Not a sound from the Toroids.

Switching off one toroid and FET drive under 2.5kw of load is a nothing event.  

BTW I set it up with 2 x 10 ohm NTCs in series one in each PCB location, so a total of 40 Ohm I will try 2 x 10 tomorrow if you like.

Tried and heading over for a break in a short while.

I hope that is of some help
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wiseguy

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Posted: 11:02am 12 Sep 2024
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Thanks Mike you may well know that depending on how the second Toroid turns off and where it is in the cycle, combined with when RE1 then closes and powers it up again also at the right (worst) point in the cycle for a peak current event to occur. So sometimes it will be imperceptible other times a bump and maybe 10 - 20 complete test cycles of off and then on again to find a more major bump or two.

What really interests me is how long the DC (or AC) current surge lasts for in the worst case "bump".  Further analysis & testing with my temporary setup (using mains) revealed to me that it seems to be 80% all over in ~ 1 or 2 cycles and for the last 20% idling normally after maybe 10 cycles maximum.  This means I could probably tweak the first monostable timing down from ~2 seconds to maybe as low as 100 - 250 milliseconds. Meaning that a major start surge is being assisted by the second Toroid within a quarter of a second without a major toroid "thump".

By the way, very brave of you to try this all connected to the major 48V batteries, I admire your confidence. Your description of its performance and effect is what I had expected but confirmation is pleasing.  What Value of inrush limiter did you use, I got 15R units and there will be 2 in series. ?

Note to Cpoc; I bench tested the sensing and timing circuits controlling the relays which all worked well, now from KeepIS's test results, it indicates the complete circuitry will work just fine and as expected. Does this mean you are comfortable for me to order some PCBs for your inverter (and for a few others) soon ?  I won't order though until we have discussed further any refinements etc & under my post not KeepIS's.
If at first you dont succeed, I suggest you avoid sky diving....
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KeepIS

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Posted: 07:03pm 12 Sep 2024
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I was thinking about this last night and I realized that monitoring the Peak DC input current is not going to work correctly for this test.

It's the same reason why the first One or Two cycle a big load is not at full current through the Hall sensors, it's because half of the first two cycles of current surge is partly supplied by the Capacitor Banks on the Power Board.

It's the same when monitoring Stage-1 current during the Stage-2 enable cycle.

Example: I have a 53V Power supply that is current limited to 1A, the Inverter is running Power Board 1 only.

When the second Toroid is AC coupled (paralleled) the Power supply current never trips. The Peak DC input current indicates 10A, but that 10A is actually coming from the Power board Caps on "Stage-2", and the current spike supplied by the Stage-1 caps is hidden from the Hall sensors as well.

I will use a Peak Hold AC clamp meter at the AC output of Stage-1 and try to get a correct reading of Stage-1 AC load during the Stage-2 power enable cycle.

I actually tried switching as fast as I could through the Pre-Flux position, many times in a row, it really didn't bother it at all, occasionally got a slightly higher pulse, but nothing really.

So I agree, it looks like it does not need much time to get the flux in the right direction.

I will investigate in more detail this morning, I have a few interesting test to do.

  Quote   What Value of inrush limiter did you use, I got 15R units and there will be 2 in series. ?

From the end of my previous post:

I set it up with 2 x 10R NTCs in series, so 20R in each PCB location for a total of 40R  

I'll try with lower values today and compare.
_
Edited 2024-09-13 05:16 by KeepIS
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KeepIS

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Posted: 11:50pm 12 Sep 2024
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My suspicions were correct:

I remembered back to the tests I did changing the residual flux of the Toriod with the flick of 1.3v cell, which changes the so called Cap+Toroid "Resonance frequency" by -30Hz to +100Hz for the same value of secondary Cap.

Step 1:
I replaced each NTC position with two 47R 5W resistors - they could be 1 watt if using a small delay, however as I'm manually switching and can hold the Pre-Flux state for any amount of time, I used higher wattage R for this test.

I chose a high total value of around 100R because I wanted to verify the possibility that all we are really doing is just getting the Stage-2 Toroid to play nice before connecting it across the AC output of Stage-1, and not trying to get it to 240AC.  

Step 2: I removed the Capacitor boards from Power Board 1, I replaced them with a 10uF AC CAP, this 10uF cap was to help dampen any ringing and noise when running the 1st Power Stage without CAP boards.

CAP boards were removed so that the Hall DC current sensors would register the TRUE current drawn by Power Board 1, and not be fooled by the CAP bank discharge current.

The Result:

Nothing much changed - Current draw through 94 ohms is very low in the Pre-Flux stage.

Delaying a second or so before closing RL2 (shorting the Resistors) was exactly the same as before.

Flicking the switch as fast as I could from off to RL2 energized made a worst case 50A PEAK draw, but 5 out of 8 times it would hardly resister a current reading, but with a load there is hardly any current spike when switching as fast as I can, and for as many times as I tried.

The 2nd Toroid appears to prefer a fast Pre-Flux time, 200ms to 300ms I think wiseguy was thinking of and that sounds about right, a longer time has no benefit and sometimes causes a slight current spike on the DC peak meter.  

Stage-1 Idles at 31 watts - it's powering the Inverter electronics including my small fans etc.

Switching Stage-2 on only increases Idle power by 21W, which from memory is around the magnetizing power I measure for these stacked Toroids on the bench - I will have to check.

EDIT:

I've been running the property off grid on the Inverter for a few hours, every 10 minutes switching the 2nd stage off, a minute later back on (quickly), not a single current spike or problem.

My Conclusion:

It appears that all mine needs is a little burst of Toroid-1 AC into the 2nd Toroid to set its residual flux up for low current paralleling of both Toroids.

FYI I just tried the large Variac "A Very heavy Toroid" it drew a Peak of 300A on the first turn on, and 600 Amperes the second time.

This Dual Inverter is set to trip at a conservative Peak DC current of 940 Amperes.      

It laughed at the 600A Variac
_
Edited 2024-09-13 13:44 by KeepIS
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Mike.
 
wiseguy

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Posted: 04:17am 13 Sep 2024
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I just noticed after I wrote this you have edited the original so we are on a similar course.

I think I was not very clear on what I was trying to see, your recent feedback probably helped to further clarify what is needed. The result of trying to drive a saturated Toroid for 1 cycle could look like the following.

Assume Toroid 1 & 2 primary resistance = 0.1R (mine is 96milliohms), assume toroid 2 is left magnetised in one direction and it starts at the worst possible time to be driven further into hard saturation. The following examples remember are only for the first cycle the next cycle is typically 80+% less.

The sums would look like I = E/R =240/0.2 = 1200A AC, passed through a 1:8 turns ratio = 9600A on the primary.
(this will not be the case in real life assume only ~ maybe 50% of this or less. This sum result is really a nonsense figure due to the 240V circuit impedances ie another 0.1R reduces 1200A to 800A and some of the energy will further saturate the core to a degree, also given AC = 340V peak results would be even worse than 240 used)
The main point is to illustrate and emphasise a lot of amps for a cycle or two. Your edited post suggests an AC current occurred with the Variac somewhere north of 100A ?

For 94R I = 240/94 or 2.5A AC passed through a 1:8 turns ratio = 20A on the primary or around 480 times less.

For 30R I = 240/30 = 8A AC passed through a 1:8 turns ratio = 64A on the primary or around 150 times less.

The 94R would be hard to find the peak current as worst possible case is limited to 2.5A.

So I think the best way to test is to use the AC current measure and use a total of 20 - 30R maximum for the NTC. Any self heating of an NTC inrush limiter after the first big bump would serve to reduce the series R speeding up the degaussing of the saturation peak, a fixed resistor will be close enough for approximate results though.

I would also leave the input capacitors as normal in place to assist with the low impedance surge measurement of whatever the mains peak will be.  I agree the capacitors will mask the input DC bump to a large degree, but the FETs will still have to provide whatever impedance the coupling of the 2 toroids will cause.  Given the size of your primary wiring with or without the capacitors will probably not make a lot of difference to the  FETs peak current which ultimately is what we want to minimise to a reasonable value.

Thanks for your help to date to test & evaluate the second stage behaviour. If you have an excess of 47Rs Maybe just use 2 x 47Rs in parallel across each existing 47R making 2 x 15R or 30R total will provide better indicative data.
Edited 2024-09-13 14:39 by wiseguy
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KeepIS

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Posted: 04:44am 13 Sep 2024
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For AC current, I found the Peak Clamp meter I had was no good, lowest range is 200A and it showed nothing on peak hold into the 2nd Toriod.

I should have set up one of the little current transformers, but I'm just running out of time at the moment.

I've removed the 2 stage switch and connected the Inverter back to a straight Dual stage Inverter.

Now I need to build a second Nano 7 controller as a spare whilst I'm in the building frame of mind.

A dozen or so household repairs and yard work that I've neglected for the past 2 months also await me    

But at least the switching method you came up with is sound

EDIT

I forgot to add, that Variac will throw the Mains circuit breaker when a peak surge like that happens on Mains power.

The Variac is the only thing - apart from a short, that will throw the Mains breaker.

I intend to try a similar test startup on that Variac, and see what it takes to make it play nice, I plan to make the Electronic Variac - one day.    
_
Edited 2024-09-13 15:23 by KeepIS
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KeepIS

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Posted: 08:23am 13 Sep 2024
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  Quote  Your edited post suggests an AC current occurred with the Variac somewhere north of 100A ?


I guess it may have been getting close to that if the calculations are correct, and allowing for parallax errors at a distance of 2 meters looking at two analogue meters kiss 300A each.

Inverter AC current trip is set at 48A on each power stage, so AC trip is at 96A, and allowing for AC voltage drop at those transient peaks, I guess that might be somewhere around 18 or 19kW ?
Edited 2024-09-13 18:24 by KeepIS
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phil99

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  Quote  test startup on that Variac, and see what it takes to make it play nice

The problem with Variacs is the margin between the normal peak magnetizing current and saturation current is small. They do that to keep the size, weight and cost down.

An air-cored inductor (ie one where residual flux does not exist and saturation can't happen)  will reach a peak current twice the normal peak current if switched on at the 0V point in a cycle. If switched on then the current has an entire half cycle to keep rising.
Add a core that saturates well below double and the peak current goes through the roof.

HV distribution transformers have more than 100% margin to ensure saturation never happens.

Switching on at peak volts only gives the current a quarter cycle to rise before the voltage reverses and pulls it back down.
In steady state operation current lags voltage by 90° so the inductor current is 0A when the voltage is at Vmax. Switching on at Vmax recreates that right from the beginning.

Residual magnetism can contribute a little more but they have good quality GOSS which holds little residual.

Your own experiment shows a 1.5V cell can reverse it in a quality toroid.
A great deal of work went into minimizing residual magnetism in GOSS as having to reverse the residual every half cycle causes a power loss.
Look up B-H curve Hysteresis Loop. The points where that loop crosses the B axis are the residual magnetism. The area enclosed within the loop is proportional to the energy lost in each cycle.

Your cores run cold indicating there is little power lost there and therefore little residual magnetism.

The key is to switch on close to peak volts, then the inrush is negligible.

In the battery charger section of a 50kW UPS each phase was switched on in turn at peak volts resulting in no measurable surge at all.
 
analog8484
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  phil99 said  
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Your cores run cold indicating there is little power lost there and therefore little residual magnetism.



Interesting point.
 
KeepIS

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Thanks phill99 for the Input:

  Quote  The problem with Variacs is the margin between the normal peak magnetizing current and saturation current is small. They do that to keep the size, weight and cost down.

Unfortunately they failed with this Variac, its size and weigh match a big Aerosharp Core, for me, the simplest solution for it is an NTC and bypass relay, that worked.

Or a beefy Inverter that will happily give the Variac the middle finger  

  Quote  Your cores run cold indicating there is little power lost there and therefore little residual magnetism.

They do run at room temperature at power levels up to 3kw in each Toroid -- BUT -- that is with continuous enhanced convection air flow, and Toroids wound and mounted to take full advantage of this assisted natural air flow scheme.

Without that airflow, at the same power levels they would feel warm to touch and around 43° and slowly rise with extended running time without full forced Toroid Cooling.

Most of that heat is from the 14 turn SPWM Drive windings, same for the 4 chokes, just cable heating. The above assisted airflow system completely removes that heat, but at the expense of an extra 13w added to the Running power (gasp!)

I say running power because this Inverter never actually idles.

With respect to your info on residual magnetism, this does appear to be the case.

The current peak is way less than I had anticipated, when simply connecting the second Toriod across the the primary running Toroid without a series NTC with bypass, the current was still relatively low.

However this Inverter is hardwired as a dedicated continuous 10kW unit, so the  switching current isn't a consideration for me.

The test was interesting to do though, as it shows how smoothly this function works when used with wiseguys Dual Toroid & Dual Power Board Inverter design.

If I were someone building a single stage Inverter right now, I'd make sure to leave enough room for a simple upgrade to a Dual Toroid higher power Inverter in the future.  
_
_
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Revlac

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Posted: 12:34pm 14 Sep 2024
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  Quote  I'd make sure to leave enough room for a simple upgrade to a Dual Toroid higher power Inverter in the future.  

I just checked,  I have enough room for 2 power boards.
Cheers Aaron
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KeepIS

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Posted: 11:42pm 14 Sep 2024
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Ha, I just knew you would have
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