Guru
Joined: 13/10/2014
Location: AustraliaPosts: 1860
| Posted: 04:22am 25 May 2023 |
Another ramble, but more to give an idea of where I'm coming from mentally at this stage of the inverter build, which is virtually completed. I'm moving on to make a few Solar regulators, and make a few of my Hot Water system controllers for friends who want to connect some reclaimed old solar panels to run their existing 240vAC HW units, price of power is literally going through the roof for some of them. Then I want to make a backup set of Controller and Power boards for the inverter.
The bad loads, it depends on the definition of severe, the sound definitely is, but it doesn't take much to make a Toriod talk. The Inverter AC waveforms may simply have a small kink in one side, sometimes with a bit of ringing, and as you are aware, the value of choke to quieten every load may not allow the same Inverter to survive very long under repeated transient 25+kW loads. BTW, running basic household devices will see over 12kW DC peaks into an inverter, that's not a guess, that's a fact that I constantly monitor. It takes very little to do that. You may also end up chasing your tail trying to get consistent meaningful capture of these AC loads conditions, especially with the equipment that only a few of us may have available to actually do that clearly, and usually that equipment will be in the lower cost range of test gear.
If these inverters were factory produced, they would all behave the same, the only variance would be the DC supply, cabling and Loads, any value of components chosen to solve a problem in one, would apply to all.
If you take all the relevant factors you bought up, and appreciated BTW, then add even more interactions in the magnetic interplay of widely varying toriod builds, the current and drive requirements for both the effect it has on the magnetics, and the effects all of this has on the problem of keeping the FETS we use, or can afford to use, from self destruction, and then throw into the mix, hand wound and user constructed toriods from junk inverters of various types, welders, variacs, etc, and winding transformers that are different in so many ways.
I really feel that trying to find a definitive answer that is constant and applicable to all hobby built inverters, with the equipment we hobbyists have, and while there is still debate on the best drive system, gate resistance, board design, layout, FET, resonance point, current protection, failure modes, and on and on, is something I don't really have the time or equipment to do.
Within the limited resources available, I think most of us try to document our own build observations in the hope that others, some with real understanding, experience and even training in various fields (some quite complex) of thermal, electronic and magnetic theory and likely ones I've missed, which all combine to make a powerful inverter, can either shed light on what we observe happening in our builds, or that our observations may help new builders to at least have an insight into the way these inverters are constructed, and the problems encountered in building one.
Once again, and right on cue, another spanner is thrown into the works.
The EMF produced by my inverter in my HF radio equipment has now increased from nothing to pretty dam bad - what changed - I changed chokes, in particular that small Ferrite core.
So now I have to drag out my spectrum analyzer, see what I'm looking at, hope splitting the big choke for each leg reduces it somewhat, and then likely set about designing an RF filter while finding the exact mode of injection or radiation paths into the external communications equipment, which is something akin to herding cats.
As I sit here typing, there have been five 500A peak DC load startups, each a full 2.5 seconds of solid 500A, followed by another half dozen 290A DC startup loads each time, the UPS is silent! the inverter is silent!
How do I know they started ? Exactly the same way when running on Mains AC, the "slightest" flick in the LED fluorescent lights above, and slightly in front of me, if I was walking around the work area I likely wouldn't even notice.
BTW, Inverter has been running nonstop for days now without a single fan startup, and the Toriod temperature managed to reach a staggering 30.6 deg C a few minutes ago, and that's running inside a warm man cave.
.